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Dmitry A Storchak - One of the best experts on this subject based on the ideXlab platform.
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the isc gem Earthquake Catalogue 1904 2014 status after the extension project
Earth System Science Data, 2018Co-Authors: Domenico Di Giacomo, Robert E Engdahl, Dmitry A StorchakAbstract:Abstract. We outline the work done to extend and improve the ISC-GEM Global Instrumental Earthquake Catalogue, a dataset which was first released in 2013 ( Storchak et al. , 2013 , 2015 ) . In its first version (V1) the Catalogue included global Earthquakes selected according to time-dependent cut-off magnitudes: 7.5 and above between 1900 and 1918 (plus significant continental Earthquakes 6.5 and above); 6.25 between 1918 and 1959; 5.5 between 1960 and 2009. Such selection criteria were dictated by time and resource limitations. With the Extension Project we added both pre-1960 events below the original cut-off magnitudes (if enough station data were available to perform relocation and magnitude recomputation) and added events with magnitude 5.5 and above from 2010 to 2014. The project ran over a 4-year period during which a new version of the ISC-GEM Catalogue was released each year via the ISC website ( http://http://www.isc.ac.uk/iscgem/ , last access: 10 October 2018). For each year, not only have we added new events to the Catalogue for a given time range but also revised events already in V1 if additional data became available or location and/or magnitude reassessments were required. Here we recall the general background behind the production of the ISC-GEM Catalogue and describe the features of the different periods in which the Catalogue has been extended. Compared to the 2013 release, we eliminated Earthquakes during the first 4 years (1900–1903) of the Catalogue (due to lack of reliable station data), added approximately 12 000 and 2500 Earthquakes before 1960 and between 2010 and 2014, respectively, and improved the solution for approximately 2000 Earthquakes already listed in previous versions. We expect the ISC-GEM Catalogue to continue to be one of the most useful datasets for studies of the Earth's global seismicity and an important benchmark for seismic hazard analyses, and, ultimately, an asset for the seismological community as well as other geoscience fields, education and outreach activities. The ISC-GEM Catalogue is freely available at https://doi.org/10.31905/D808B825 .
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isc gem global instrumental Earthquake Catalogue 1900 2009 i data collection from early instrumental seismological bulletins
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Domenico Di Giacomo, J S Harris, Antonio Villasenor, Dmitry A Storchak, Robert E Engdahl, William H K LeeAbstract:Abstract In order to produce a new global reference Earthquake Catalogue based on instrumental data covering the last 100+ years of global Earthquakes, we collected, digitized and processed an unprecedented amount of printed early instrumental seismological bulletins with fundamental parametric data for relocating and reassessing the magnitude of Earthquakes that occurred in the period between 1904 and 1970. This effort was necessary in order to produce an Earthquake Catalogue with locations and magnitudes as homogeneous as possible. The parametric data obtained and processed during this work fills a large gap in electronic bulletin data availability. This new dataset complements the data publicly available in the International Seismological Centre (ISC) Bulletin starting in 1964. With respect to the amplitude-period data necessary to re-compute magnitude, we searched through the global collection of printed bulletins stored at the ISC and entered relevant station parametric data into the database. As a result, over 110,000 surface and body-wave amplitude-period pairs for re-computing standard magnitudes M S and m b were added to the ISC database. To facilitate Earthquake relocation, different sources have been used to retrieve body-wave arrival times. These were entered into the database using optical character recognition methods (International Seismological Summary, 1918–1959) or manually (e.g., British Association for the Advancement of Science, 1913–1917). In total, ∼1,000,000 phase arrival times were added to the ISC database for large Earthquakes that occurred in the time interval 1904–1970. The selection of Earthquakes for which data was added depends on time period and magnitude: for the early years of last century (until 1917) only very large Earthquakes were selected for processing ( M ⩾ 7.5), whereas in the periods 1918–1959 and 1960–2009 the magnitude thresholds are 6.25 and 5.5, respectively. Such a selection was mainly dictated by limitations in time and funding. Although the newly available parametric data is only a subset of the station data available in the printed bulletins, its electronic availability will be important for any future study of Earthquakes that occurred during the early instrumental period.
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the isc gem global instrumental Earthquake Catalogue 1900 2009 introduction
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Dmitry A Storchak, Domenico Di Giacomo, J S Harris, William H K Lee, E R Engdahl, Istvan Bondar, Peter Bormann, Antonio VillasenorAbstract:Abstract In this introductory article we give a general description of the ISC-GEM Global Instrumental Earthquake Catalogue (1900–2009). We also provide the background for four further articles that describe the effort in collecting and digitizing parametric Earthquake bulletin data as well as the methodologies developed to compute homogeneous Earthquake parameters. The result of the two and a half year project is a Catalogue of approximately 20,000 large Earthquakes covering 110 years with hypocentres and uncertainties computed using the same technique and velocity model. We show that the overall homogeneity of the main Earthquake parameters in the Catalogue was achieved despite changes in instrumentation and routine measurement practices concurrent with developments in instrumental seismology from almost a ground level to its current state. For each Earthquake, MW magnitude values and uncertainties were computed either based on available estimates of seismic moment or using new empirical relationships between MW, MS and mb. Further important results of this project include the electronic availability of a considerable volume of seismic wave arrival time and amplitude measurements from early instrumental printed station bulletins. These newly recovered amplitude measurements provided a basis for computation of many previously unavailable MS magnitudes with uncertainties. In this article we describe why such a Catalogue is required for a comprehensive assessment of global and regional seismic hazard. We also describe other potential uses of the Catalogue in many other fields of Earth Sciences. We discuss the Catalogue availability and lay out the plans of further development.
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isc gem global instrumental Earthquake Catalogue 1900 2009 ii location and seismicity patterns
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Istvan Bondar, J S Harris, Antonio Villasenor, Robert E Engdahl, Dmitry A StorchakAbstract:Abstract We present the final results of a two-year project sponsored by the Global Earthquake Model (GEM) Foundation. The ISC-GEM global Catalogue consists of some 19 thousand instrumentally recorded, moderate to large Earthquakes, spanning 110 years of seismicity. We relocated all events in the Catalogue using a two-tier approach. The EHB location methodology (Engdahl et al., 1998) was applied first to obtain improved hypocentres with special focus on the depth determination. The locations were further refined in the next step by fixing the depths to those from the EHB analysis and applying the new International Seismological Centre (ISC) location algorithm (Bondar and Storchak, 2011) that reduces location bias by accounting for correlated travel-time prediction error structure. To facilitate the relocation effort, some one million seismic P and S wave arrival-time data were added to the ISC database for the period between 1904 and 1970, either from original station bulletins in the ISC archive or by digitizing the scanned images of the International Seismological Summary (ISS) bulletin (Villasenor and Engdahl, 2005, 2007). Although no substantial amount of new phase data were acquired for the modern period (1964–2009), the number of phases used in the location has still increased by three millions, owing to fact that both the EHB and ISC locators use most well-recorded ak135 (Kennett et al., 1995) phases in the location. We show that the relocation effort yielded substantially improved locations, especially in the first half of the 20th century; we demonstrate significant improvements in focal depth estimates in subduction zones and other seismically active regions; and we show that the ISC-GEM Catalogue provides an improved view of 110 years of global seismicity of the Earth. The ISC-GEM Global Instrumental Earthquake Catalogue represents the final product of one of the ten global components in the GEM program, and is available to researchers at the ISC ( www.isc.ac.uk ) website.
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isc gem global instrumental Earthquake Catalogue 1900 2009 iii re computed ms and mb proxy mw final magnitude composition and completeness assessment
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Domenico Di Giacomo, Dmitry A Storchak, Robert E Engdahl, Istvan Bondar, Peter Bormann, J S HarrisAbstract:Abstract This paper outlines the re-computation and compilation of the magnitudes now contained in the final ISC-GEM Reference Global Instrumental Earthquake Catalogue (1900–2009). The Catalogue is available via the ISC website ( www.isc.ac.uk/iscgem/ ) and lists in a comma separated format the location and magnitude parameters (with corresponding uncertainties) of global large Earthquakes. In this work we report on the procedures adopted to obtain the final magnitude composition of the nearly 20,000 Earthquakes processed. We have made every effort to use uniform procedures of magnitude determination throughout the entire period of the Catalogue. The re-computation of the surface wave MS and short-period body-wave mb values benefitted from new hypocentres (Bondar et al., 2015), previously unavailable amplitude-period data digitized during this project (Di Giacomo et al., 2015), and a more reliable algorithm for magnitude estimation based on a 20% alpha-trimmed median magnitude (Bondar and Storchak, 2011). In particular, for MS until the end of 1970 we have processed an unprecedented amount of data and obtained several thousands of station magnitudes not available before. The available re-computed MS and mb provided an ideal basis for deriving new conversion relationships to moment magnitude MW. Therefore, rather than using previously published regression models, we derived new empirical relationships using both generalized orthogonal linear and exponential non-linear models to obtain MW proxies from MS and mb. The new models were tested against true values of MW, and the newly derived exponential models were then preferred to the linear ones in computing MW proxies. For the final magnitude composition of the ISC-GEM Catalogue, we preferred directly measured MW values as published by the Global CMT project for the period 1976–2009 (plus intermediate-depth Earthquakes between 1962 and 1975). In addition, over 1000 publications have been examined to obtain direct seismic moment M0 and, therefore, also MW estimates for 967 large Earthquakes during 1900–1978 (Lee and Engdahl, 2015) by various alternative methods to the current GCMT procedure. In all other instances we computed MW proxy values by converting our re-computed MS and mb values into MW, using the newly derived non-linear regression models. The final magnitude composition is an improvement in terms of magnitude homogeneity compared to previous Catalogues. The magnitude completeness is not homogeneous over the 110 years covered by the ISC-GEM Catalogue. Therefore, seismicity rate estimates may be strongly affected without a careful time window selection. In particular, the ISC-GEM Catalogue appears to be complete down to MW 5.6 starting from 1964, whereas for the early instrumental period the completeness varies from ∼7.5 to 6.2. Further time and resources would be necessary to homogenize the magnitude of completeness over the entire Catalogue length.
Robert E Engdahl - One of the best experts on this subject based on the ideXlab platform.
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the isc gem Earthquake Catalogue 1904 2014 status after the extension project
Earth System Science Data, 2018Co-Authors: Domenico Di Giacomo, Robert E Engdahl, Dmitry A StorchakAbstract:Abstract. We outline the work done to extend and improve the ISC-GEM Global Instrumental Earthquake Catalogue, a dataset which was first released in 2013 ( Storchak et al. , 2013 , 2015 ) . In its first version (V1) the Catalogue included global Earthquakes selected according to time-dependent cut-off magnitudes: 7.5 and above between 1900 and 1918 (plus significant continental Earthquakes 6.5 and above); 6.25 between 1918 and 1959; 5.5 between 1960 and 2009. Such selection criteria were dictated by time and resource limitations. With the Extension Project we added both pre-1960 events below the original cut-off magnitudes (if enough station data were available to perform relocation and magnitude recomputation) and added events with magnitude 5.5 and above from 2010 to 2014. The project ran over a 4-year period during which a new version of the ISC-GEM Catalogue was released each year via the ISC website ( http://http://www.isc.ac.uk/iscgem/ , last access: 10 October 2018). For each year, not only have we added new events to the Catalogue for a given time range but also revised events already in V1 if additional data became available or location and/or magnitude reassessments were required. Here we recall the general background behind the production of the ISC-GEM Catalogue and describe the features of the different periods in which the Catalogue has been extended. Compared to the 2013 release, we eliminated Earthquakes during the first 4 years (1900–1903) of the Catalogue (due to lack of reliable station data), added approximately 12 000 and 2500 Earthquakes before 1960 and between 2010 and 2014, respectively, and improved the solution for approximately 2000 Earthquakes already listed in previous versions. We expect the ISC-GEM Catalogue to continue to be one of the most useful datasets for studies of the Earth's global seismicity and an important benchmark for seismic hazard analyses, and, ultimately, an asset for the seismological community as well as other geoscience fields, education and outreach activities. The ISC-GEM Catalogue is freely available at https://doi.org/10.31905/D808B825 .
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isc gem global instrumental Earthquake Catalogue 1900 2009 i data collection from early instrumental seismological bulletins
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Domenico Di Giacomo, J S Harris, Antonio Villasenor, Dmitry A Storchak, Robert E Engdahl, William H K LeeAbstract:Abstract In order to produce a new global reference Earthquake Catalogue based on instrumental data covering the last 100+ years of global Earthquakes, we collected, digitized and processed an unprecedented amount of printed early instrumental seismological bulletins with fundamental parametric data for relocating and reassessing the magnitude of Earthquakes that occurred in the period between 1904 and 1970. This effort was necessary in order to produce an Earthquake Catalogue with locations and magnitudes as homogeneous as possible. The parametric data obtained and processed during this work fills a large gap in electronic bulletin data availability. This new dataset complements the data publicly available in the International Seismological Centre (ISC) Bulletin starting in 1964. With respect to the amplitude-period data necessary to re-compute magnitude, we searched through the global collection of printed bulletins stored at the ISC and entered relevant station parametric data into the database. As a result, over 110,000 surface and body-wave amplitude-period pairs for re-computing standard magnitudes M S and m b were added to the ISC database. To facilitate Earthquake relocation, different sources have been used to retrieve body-wave arrival times. These were entered into the database using optical character recognition methods (International Seismological Summary, 1918–1959) or manually (e.g., British Association for the Advancement of Science, 1913–1917). In total, ∼1,000,000 phase arrival times were added to the ISC database for large Earthquakes that occurred in the time interval 1904–1970. The selection of Earthquakes for which data was added depends on time period and magnitude: for the early years of last century (until 1917) only very large Earthquakes were selected for processing ( M ⩾ 7.5), whereas in the periods 1918–1959 and 1960–2009 the magnitude thresholds are 6.25 and 5.5, respectively. Such a selection was mainly dictated by limitations in time and funding. Although the newly available parametric data is only a subset of the station data available in the printed bulletins, its electronic availability will be important for any future study of Earthquakes that occurred during the early instrumental period.
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isc gem global instrumental Earthquake Catalogue 1900 2009 ii location and seismicity patterns
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Istvan Bondar, J S Harris, Antonio Villasenor, Robert E Engdahl, Dmitry A StorchakAbstract:Abstract We present the final results of a two-year project sponsored by the Global Earthquake Model (GEM) Foundation. The ISC-GEM global Catalogue consists of some 19 thousand instrumentally recorded, moderate to large Earthquakes, spanning 110 years of seismicity. We relocated all events in the Catalogue using a two-tier approach. The EHB location methodology (Engdahl et al., 1998) was applied first to obtain improved hypocentres with special focus on the depth determination. The locations were further refined in the next step by fixing the depths to those from the EHB analysis and applying the new International Seismological Centre (ISC) location algorithm (Bondar and Storchak, 2011) that reduces location bias by accounting for correlated travel-time prediction error structure. To facilitate the relocation effort, some one million seismic P and S wave arrival-time data were added to the ISC database for the period between 1904 and 1970, either from original station bulletins in the ISC archive or by digitizing the scanned images of the International Seismological Summary (ISS) bulletin (Villasenor and Engdahl, 2005, 2007). Although no substantial amount of new phase data were acquired for the modern period (1964–2009), the number of phases used in the location has still increased by three millions, owing to fact that both the EHB and ISC locators use most well-recorded ak135 (Kennett et al., 1995) phases in the location. We show that the relocation effort yielded substantially improved locations, especially in the first half of the 20th century; we demonstrate significant improvements in focal depth estimates in subduction zones and other seismically active regions; and we show that the ISC-GEM Catalogue provides an improved view of 110 years of global seismicity of the Earth. The ISC-GEM Global Instrumental Earthquake Catalogue represents the final product of one of the ten global components in the GEM program, and is available to researchers at the ISC ( www.isc.ac.uk ) website.
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bibliographical search for reliable seismic moments of large Earthquakes during 1900 1979 to compute mw in the isc gem global instrumental reference Earthquake Catalogue
Physics of the Earth and Planetary Interiors, 2015Co-Authors: William H K Lee, Robert E EngdahlAbstract:Abstract Moment magnitude ( M W ) determinations from the online GCMT Catalogue of seismic moment tensor solutions (GCMT Catalog, 2011) have provided the bulk of M W values in the ISC-GEM Global Instrumental Reference Earthquake Catalogue (1900–2009) for almost all moderate-to-large Earthquakes occurring after 1975. This paper describes an effort to determine M W of large Earthquakes that occurred prior to the start of the digital seismograph era, based on credible assessments of thousands of seismic moment ( M 0 ) values published in the scientific literature by hundreds of individual authors. M W computed from the published M 0 values (for a time period more than twice that of the digital era) are preferable to proxy M W values, especially for Earthquakes with M W greater than about 8.5, for which M S is known to be underestimated or “saturated”. After examining 1,123 papers, we compile a database of seismic moments and related information for 1,003 Earthquakes with published M 0 values, of which 967 were included in the ISC-GEM Catalogue. The remaining 36 Earthquakes were not included in the Catalogue due to difficulties in their relocation because of inadequate arrival time information. However, 5 of these Earthquakes with bibliographic M 0 (and thus M W ) are included in the Catalogue’s Appendix. A search for reliable seismic moments was not successful for Earthquakes prior to 1904. For each of the 967 Earthquakes a “preferred” seismic moment value (if there is more than one) was selected and its uncertainty was estimated according to the data and method used. We used the IASPEI formula (IASPEI, 2005) to compute direct moment magnitudes ( M W [ M 0 ]) based on the seismic moments ( M 0 ), and assigned their errors based on the uncertainties of M 0 . From 1900 to 1979, there are 129 great or near great Earthquakes ( M W ⩾ 7.75) – the bibliographic search provided direct M W values for 86 of these events (or 67%), the GCMT Catalog provided direct M W values for 8 events (or 6%), and the remaining 35 (or 27%) Earthquakes have empirically determined proxy M W estimates. An electronic supplementary file is included with this paper in order to provide our M 0 / M W Catalogue of Earthquakes (1904–1978) from the published literature, and a reference list of the 1,123 papers that we examined.
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isc gem global instrumental Earthquake Catalogue 1900 2009 iii re computed ms and mb proxy mw final magnitude composition and completeness assessment
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Domenico Di Giacomo, Dmitry A Storchak, Robert E Engdahl, Istvan Bondar, Peter Bormann, J S HarrisAbstract:Abstract This paper outlines the re-computation and compilation of the magnitudes now contained in the final ISC-GEM Reference Global Instrumental Earthquake Catalogue (1900–2009). The Catalogue is available via the ISC website ( www.isc.ac.uk/iscgem/ ) and lists in a comma separated format the location and magnitude parameters (with corresponding uncertainties) of global large Earthquakes. In this work we report on the procedures adopted to obtain the final magnitude composition of the nearly 20,000 Earthquakes processed. We have made every effort to use uniform procedures of magnitude determination throughout the entire period of the Catalogue. The re-computation of the surface wave MS and short-period body-wave mb values benefitted from new hypocentres (Bondar et al., 2015), previously unavailable amplitude-period data digitized during this project (Di Giacomo et al., 2015), and a more reliable algorithm for magnitude estimation based on a 20% alpha-trimmed median magnitude (Bondar and Storchak, 2011). In particular, for MS until the end of 1970 we have processed an unprecedented amount of data and obtained several thousands of station magnitudes not available before. The available re-computed MS and mb provided an ideal basis for deriving new conversion relationships to moment magnitude MW. Therefore, rather than using previously published regression models, we derived new empirical relationships using both generalized orthogonal linear and exponential non-linear models to obtain MW proxies from MS and mb. The new models were tested against true values of MW, and the newly derived exponential models were then preferred to the linear ones in computing MW proxies. For the final magnitude composition of the ISC-GEM Catalogue, we preferred directly measured MW values as published by the Global CMT project for the period 1976–2009 (plus intermediate-depth Earthquakes between 1962 and 1975). In addition, over 1000 publications have been examined to obtain direct seismic moment M0 and, therefore, also MW estimates for 967 large Earthquakes during 1900–1978 (Lee and Engdahl, 2015) by various alternative methods to the current GCMT procedure. In all other instances we computed MW proxy values by converting our re-computed MS and mb values into MW, using the newly derived non-linear regression models. The final magnitude composition is an improvement in terms of magnitude homogeneity compared to previous Catalogues. The magnitude completeness is not homogeneous over the 110 years covered by the ISC-GEM Catalogue. Therefore, seismicity rate estimates may be strongly affected without a careful time window selection. In particular, the ISC-GEM Catalogue appears to be complete down to MW 5.6 starting from 1964, whereas for the early instrumental period the completeness varies from ∼7.5 to 6.2. Further time and resources would be necessary to homogenize the magnitude of completeness over the entire Catalogue length.
Domenico Di Giacomo - One of the best experts on this subject based on the ideXlab platform.
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the isc gem Earthquake Catalogue 1904 2014 status after the extension project
Earth System Science Data, 2018Co-Authors: Domenico Di Giacomo, Robert E Engdahl, Dmitry A StorchakAbstract:Abstract. We outline the work done to extend and improve the ISC-GEM Global Instrumental Earthquake Catalogue, a dataset which was first released in 2013 ( Storchak et al. , 2013 , 2015 ) . In its first version (V1) the Catalogue included global Earthquakes selected according to time-dependent cut-off magnitudes: 7.5 and above between 1900 and 1918 (plus significant continental Earthquakes 6.5 and above); 6.25 between 1918 and 1959; 5.5 between 1960 and 2009. Such selection criteria were dictated by time and resource limitations. With the Extension Project we added both pre-1960 events below the original cut-off magnitudes (if enough station data were available to perform relocation and magnitude recomputation) and added events with magnitude 5.5 and above from 2010 to 2014. The project ran over a 4-year period during which a new version of the ISC-GEM Catalogue was released each year via the ISC website ( http://http://www.isc.ac.uk/iscgem/ , last access: 10 October 2018). For each year, not only have we added new events to the Catalogue for a given time range but also revised events already in V1 if additional data became available or location and/or magnitude reassessments were required. Here we recall the general background behind the production of the ISC-GEM Catalogue and describe the features of the different periods in which the Catalogue has been extended. Compared to the 2013 release, we eliminated Earthquakes during the first 4 years (1900–1903) of the Catalogue (due to lack of reliable station data), added approximately 12 000 and 2500 Earthquakes before 1960 and between 2010 and 2014, respectively, and improved the solution for approximately 2000 Earthquakes already listed in previous versions. We expect the ISC-GEM Catalogue to continue to be one of the most useful datasets for studies of the Earth's global seismicity and an important benchmark for seismic hazard analyses, and, ultimately, an asset for the seismological community as well as other geoscience fields, education and outreach activities. The ISC-GEM Catalogue is freely available at https://doi.org/10.31905/D808B825 .
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isc gem global instrumental Earthquake Catalogue 1900 2009 i data collection from early instrumental seismological bulletins
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Domenico Di Giacomo, J S Harris, Antonio Villasenor, Dmitry A Storchak, Robert E Engdahl, William H K LeeAbstract:Abstract In order to produce a new global reference Earthquake Catalogue based on instrumental data covering the last 100+ years of global Earthquakes, we collected, digitized and processed an unprecedented amount of printed early instrumental seismological bulletins with fundamental parametric data for relocating and reassessing the magnitude of Earthquakes that occurred in the period between 1904 and 1970. This effort was necessary in order to produce an Earthquake Catalogue with locations and magnitudes as homogeneous as possible. The parametric data obtained and processed during this work fills a large gap in electronic bulletin data availability. This new dataset complements the data publicly available in the International Seismological Centre (ISC) Bulletin starting in 1964. With respect to the amplitude-period data necessary to re-compute magnitude, we searched through the global collection of printed bulletins stored at the ISC and entered relevant station parametric data into the database. As a result, over 110,000 surface and body-wave amplitude-period pairs for re-computing standard magnitudes M S and m b were added to the ISC database. To facilitate Earthquake relocation, different sources have been used to retrieve body-wave arrival times. These were entered into the database using optical character recognition methods (International Seismological Summary, 1918–1959) or manually (e.g., British Association for the Advancement of Science, 1913–1917). In total, ∼1,000,000 phase arrival times were added to the ISC database for large Earthquakes that occurred in the time interval 1904–1970. The selection of Earthquakes for which data was added depends on time period and magnitude: for the early years of last century (until 1917) only very large Earthquakes were selected for processing ( M ⩾ 7.5), whereas in the periods 1918–1959 and 1960–2009 the magnitude thresholds are 6.25 and 5.5, respectively. Such a selection was mainly dictated by limitations in time and funding. Although the newly available parametric data is only a subset of the station data available in the printed bulletins, its electronic availability will be important for any future study of Earthquakes that occurred during the early instrumental period.
-
the isc gem global instrumental Earthquake Catalogue 1900 2009 introduction
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Dmitry A Storchak, Domenico Di Giacomo, J S Harris, William H K Lee, E R Engdahl, Istvan Bondar, Peter Bormann, Antonio VillasenorAbstract:Abstract In this introductory article we give a general description of the ISC-GEM Global Instrumental Earthquake Catalogue (1900–2009). We also provide the background for four further articles that describe the effort in collecting and digitizing parametric Earthquake bulletin data as well as the methodologies developed to compute homogeneous Earthquake parameters. The result of the two and a half year project is a Catalogue of approximately 20,000 large Earthquakes covering 110 years with hypocentres and uncertainties computed using the same technique and velocity model. We show that the overall homogeneity of the main Earthquake parameters in the Catalogue was achieved despite changes in instrumentation and routine measurement practices concurrent with developments in instrumental seismology from almost a ground level to its current state. For each Earthquake, MW magnitude values and uncertainties were computed either based on available estimates of seismic moment or using new empirical relationships between MW, MS and mb. Further important results of this project include the electronic availability of a considerable volume of seismic wave arrival time and amplitude measurements from early instrumental printed station bulletins. These newly recovered amplitude measurements provided a basis for computation of many previously unavailable MS magnitudes with uncertainties. In this article we describe why such a Catalogue is required for a comprehensive assessment of global and regional seismic hazard. We also describe other potential uses of the Catalogue in many other fields of Earth Sciences. We discuss the Catalogue availability and lay out the plans of further development.
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isc gem global instrumental Earthquake Catalogue 1900 2009 iii re computed ms and mb proxy mw final magnitude composition and completeness assessment
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Domenico Di Giacomo, Dmitry A Storchak, Robert E Engdahl, Istvan Bondar, Peter Bormann, J S HarrisAbstract:Abstract This paper outlines the re-computation and compilation of the magnitudes now contained in the final ISC-GEM Reference Global Instrumental Earthquake Catalogue (1900–2009). The Catalogue is available via the ISC website ( www.isc.ac.uk/iscgem/ ) and lists in a comma separated format the location and magnitude parameters (with corresponding uncertainties) of global large Earthquakes. In this work we report on the procedures adopted to obtain the final magnitude composition of the nearly 20,000 Earthquakes processed. We have made every effort to use uniform procedures of magnitude determination throughout the entire period of the Catalogue. The re-computation of the surface wave MS and short-period body-wave mb values benefitted from new hypocentres (Bondar et al., 2015), previously unavailable amplitude-period data digitized during this project (Di Giacomo et al., 2015), and a more reliable algorithm for magnitude estimation based on a 20% alpha-trimmed median magnitude (Bondar and Storchak, 2011). In particular, for MS until the end of 1970 we have processed an unprecedented amount of data and obtained several thousands of station magnitudes not available before. The available re-computed MS and mb provided an ideal basis for deriving new conversion relationships to moment magnitude MW. Therefore, rather than using previously published regression models, we derived new empirical relationships using both generalized orthogonal linear and exponential non-linear models to obtain MW proxies from MS and mb. The new models were tested against true values of MW, and the newly derived exponential models were then preferred to the linear ones in computing MW proxies. For the final magnitude composition of the ISC-GEM Catalogue, we preferred directly measured MW values as published by the Global CMT project for the period 1976–2009 (plus intermediate-depth Earthquakes between 1962 and 1975). In addition, over 1000 publications have been examined to obtain direct seismic moment M0 and, therefore, also MW estimates for 967 large Earthquakes during 1900–1978 (Lee and Engdahl, 2015) by various alternative methods to the current GCMT procedure. In all other instances we computed MW proxy values by converting our re-computed MS and mb values into MW, using the newly derived non-linear regression models. The final magnitude composition is an improvement in terms of magnitude homogeneity compared to previous Catalogues. The magnitude completeness is not homogeneous over the 110 years covered by the ISC-GEM Catalogue. Therefore, seismicity rate estimates may be strongly affected without a careful time window selection. In particular, the ISC-GEM Catalogue appears to be complete down to MW 5.6 starting from 1964, whereas for the early instrumental period the completeness varies from ∼7.5 to 6.2. Further time and resources would be necessary to homogenize the magnitude of completeness over the entire Catalogue length.
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public release of the isc gem global instrumental Earthquake Catalogue 1900 2009
Seismological Research Letters, 2013Co-Authors: Dmitry A Storchak, Domenico Di Giacomo, J S Harris, Antonio Villasenor, Robert E Engdahl, William H K Lee, Istvan Bondar, Peter BormannAbstract:The International Seismological Centre–Global Earthquake Model (ISC–GEM) Global Instrumental Earthquake Catalogue (1900–2009) is the result of a special effort to substantially extend and improve currently existing global catalogs to serve the requirements of specific user groups who assess and model seismic hazard and risk. The data from the ISC–GEM Catalogue would be used worldwide yet will prove absolutely essential in those regions where a high seismicity level strongly correlates with a high population density (Fig. 1). Figure 1. Earthquakes from the ISC–GEM Catalogue in Central and South America. Lighter colors indicate shallow Earthquakes and darker colors indicate deep Earthquakes. The Catalogue is also expected to have a multidisciplinary use in a wide range of studies such as global seismicity assessment, tectonics, as well as the rapid determination of seismic hazard. Because of the large volume of digitized seismic travel‐time and amplitude data generated during this project, we expect the Catalogue to be useful in studies of the inner structure of the Earth as well as in nuclear monitoring research. This global catalog was also designed to serve as a reference to be used for calibration purposes by those compiling regional seismicity catalogs that contain events of much smaller magnitudes. This will guarantee that the catalogs prepared by other teams for different regions will contain comparable Earthquake locations and magnitude parameters, especially in border areas. The work on the Catalogue was funded by the GEM Foundation as part of the five Global Hazard Components and is a result of a 27‐month‐long project. This project was led by the ISC and performed by the team of international experts in accordance with the requirements of the Scientific Board of GEM and following recommendations of the International Association of Seismology and Physics of the Earth’s Interior (IASPEI) observers. Further, eight IT, administrative, and technical staff …
J S Harris - One of the best experts on this subject based on the ideXlab platform.
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isc gem global instrumental Earthquake Catalogue 1900 2009 i data collection from early instrumental seismological bulletins
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Domenico Di Giacomo, J S Harris, Antonio Villasenor, Dmitry A Storchak, Robert E Engdahl, William H K LeeAbstract:Abstract In order to produce a new global reference Earthquake Catalogue based on instrumental data covering the last 100+ years of global Earthquakes, we collected, digitized and processed an unprecedented amount of printed early instrumental seismological bulletins with fundamental parametric data for relocating and reassessing the magnitude of Earthquakes that occurred in the period between 1904 and 1970. This effort was necessary in order to produce an Earthquake Catalogue with locations and magnitudes as homogeneous as possible. The parametric data obtained and processed during this work fills a large gap in electronic bulletin data availability. This new dataset complements the data publicly available in the International Seismological Centre (ISC) Bulletin starting in 1964. With respect to the amplitude-period data necessary to re-compute magnitude, we searched through the global collection of printed bulletins stored at the ISC and entered relevant station parametric data into the database. As a result, over 110,000 surface and body-wave amplitude-period pairs for re-computing standard magnitudes M S and m b were added to the ISC database. To facilitate Earthquake relocation, different sources have been used to retrieve body-wave arrival times. These were entered into the database using optical character recognition methods (International Seismological Summary, 1918–1959) or manually (e.g., British Association for the Advancement of Science, 1913–1917). In total, ∼1,000,000 phase arrival times were added to the ISC database for large Earthquakes that occurred in the time interval 1904–1970. The selection of Earthquakes for which data was added depends on time period and magnitude: for the early years of last century (until 1917) only very large Earthquakes were selected for processing ( M ⩾ 7.5), whereas in the periods 1918–1959 and 1960–2009 the magnitude thresholds are 6.25 and 5.5, respectively. Such a selection was mainly dictated by limitations in time and funding. Although the newly available parametric data is only a subset of the station data available in the printed bulletins, its electronic availability will be important for any future study of Earthquakes that occurred during the early instrumental period.
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the isc gem global instrumental Earthquake Catalogue 1900 2009 introduction
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Dmitry A Storchak, Domenico Di Giacomo, J S Harris, William H K Lee, E R Engdahl, Istvan Bondar, Peter Bormann, Antonio VillasenorAbstract:Abstract In this introductory article we give a general description of the ISC-GEM Global Instrumental Earthquake Catalogue (1900–2009). We also provide the background for four further articles that describe the effort in collecting and digitizing parametric Earthquake bulletin data as well as the methodologies developed to compute homogeneous Earthquake parameters. The result of the two and a half year project is a Catalogue of approximately 20,000 large Earthquakes covering 110 years with hypocentres and uncertainties computed using the same technique and velocity model. We show that the overall homogeneity of the main Earthquake parameters in the Catalogue was achieved despite changes in instrumentation and routine measurement practices concurrent with developments in instrumental seismology from almost a ground level to its current state. For each Earthquake, MW magnitude values and uncertainties were computed either based on available estimates of seismic moment or using new empirical relationships between MW, MS and mb. Further important results of this project include the electronic availability of a considerable volume of seismic wave arrival time and amplitude measurements from early instrumental printed station bulletins. These newly recovered amplitude measurements provided a basis for computation of many previously unavailable MS magnitudes with uncertainties. In this article we describe why such a Catalogue is required for a comprehensive assessment of global and regional seismic hazard. We also describe other potential uses of the Catalogue in many other fields of Earth Sciences. We discuss the Catalogue availability and lay out the plans of further development.
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isc gem global instrumental Earthquake Catalogue 1900 2009 ii location and seismicity patterns
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Istvan Bondar, J S Harris, Antonio Villasenor, Robert E Engdahl, Dmitry A StorchakAbstract:Abstract We present the final results of a two-year project sponsored by the Global Earthquake Model (GEM) Foundation. The ISC-GEM global Catalogue consists of some 19 thousand instrumentally recorded, moderate to large Earthquakes, spanning 110 years of seismicity. We relocated all events in the Catalogue using a two-tier approach. The EHB location methodology (Engdahl et al., 1998) was applied first to obtain improved hypocentres with special focus on the depth determination. The locations were further refined in the next step by fixing the depths to those from the EHB analysis and applying the new International Seismological Centre (ISC) location algorithm (Bondar and Storchak, 2011) that reduces location bias by accounting for correlated travel-time prediction error structure. To facilitate the relocation effort, some one million seismic P and S wave arrival-time data were added to the ISC database for the period between 1904 and 1970, either from original station bulletins in the ISC archive or by digitizing the scanned images of the International Seismological Summary (ISS) bulletin (Villasenor and Engdahl, 2005, 2007). Although no substantial amount of new phase data were acquired for the modern period (1964–2009), the number of phases used in the location has still increased by three millions, owing to fact that both the EHB and ISC locators use most well-recorded ak135 (Kennett et al., 1995) phases in the location. We show that the relocation effort yielded substantially improved locations, especially in the first half of the 20th century; we demonstrate significant improvements in focal depth estimates in subduction zones and other seismically active regions; and we show that the ISC-GEM Catalogue provides an improved view of 110 years of global seismicity of the Earth. The ISC-GEM Global Instrumental Earthquake Catalogue represents the final product of one of the ten global components in the GEM program, and is available to researchers at the ISC ( www.isc.ac.uk ) website.
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isc gem global instrumental Earthquake Catalogue 1900 2009 iii re computed ms and mb proxy mw final magnitude composition and completeness assessment
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Domenico Di Giacomo, Dmitry A Storchak, Robert E Engdahl, Istvan Bondar, Peter Bormann, J S HarrisAbstract:Abstract This paper outlines the re-computation and compilation of the magnitudes now contained in the final ISC-GEM Reference Global Instrumental Earthquake Catalogue (1900–2009). The Catalogue is available via the ISC website ( www.isc.ac.uk/iscgem/ ) and lists in a comma separated format the location and magnitude parameters (with corresponding uncertainties) of global large Earthquakes. In this work we report on the procedures adopted to obtain the final magnitude composition of the nearly 20,000 Earthquakes processed. We have made every effort to use uniform procedures of magnitude determination throughout the entire period of the Catalogue. The re-computation of the surface wave MS and short-period body-wave mb values benefitted from new hypocentres (Bondar et al., 2015), previously unavailable amplitude-period data digitized during this project (Di Giacomo et al., 2015), and a more reliable algorithm for magnitude estimation based on a 20% alpha-trimmed median magnitude (Bondar and Storchak, 2011). In particular, for MS until the end of 1970 we have processed an unprecedented amount of data and obtained several thousands of station magnitudes not available before. The available re-computed MS and mb provided an ideal basis for deriving new conversion relationships to moment magnitude MW. Therefore, rather than using previously published regression models, we derived new empirical relationships using both generalized orthogonal linear and exponential non-linear models to obtain MW proxies from MS and mb. The new models were tested against true values of MW, and the newly derived exponential models were then preferred to the linear ones in computing MW proxies. For the final magnitude composition of the ISC-GEM Catalogue, we preferred directly measured MW values as published by the Global CMT project for the period 1976–2009 (plus intermediate-depth Earthquakes between 1962 and 1975). In addition, over 1000 publications have been examined to obtain direct seismic moment M0 and, therefore, also MW estimates for 967 large Earthquakes during 1900–1978 (Lee and Engdahl, 2015) by various alternative methods to the current GCMT procedure. In all other instances we computed MW proxy values by converting our re-computed MS and mb values into MW, using the newly derived non-linear regression models. The final magnitude composition is an improvement in terms of magnitude homogeneity compared to previous Catalogues. The magnitude completeness is not homogeneous over the 110 years covered by the ISC-GEM Catalogue. Therefore, seismicity rate estimates may be strongly affected without a careful time window selection. In particular, the ISC-GEM Catalogue appears to be complete down to MW 5.6 starting from 1964, whereas for the early instrumental period the completeness varies from ∼7.5 to 6.2. Further time and resources would be necessary to homogenize the magnitude of completeness over the entire Catalogue length.
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public release of the isc gem global instrumental Earthquake Catalogue 1900 2009
Seismological Research Letters, 2013Co-Authors: Dmitry A Storchak, Domenico Di Giacomo, J S Harris, Antonio Villasenor, Robert E Engdahl, William H K Lee, Istvan Bondar, Peter BormannAbstract:The International Seismological Centre–Global Earthquake Model (ISC–GEM) Global Instrumental Earthquake Catalogue (1900–2009) is the result of a special effort to substantially extend and improve currently existing global catalogs to serve the requirements of specific user groups who assess and model seismic hazard and risk. The data from the ISC–GEM Catalogue would be used worldwide yet will prove absolutely essential in those regions where a high seismicity level strongly correlates with a high population density (Fig. 1). Figure 1. Earthquakes from the ISC–GEM Catalogue in Central and South America. Lighter colors indicate shallow Earthquakes and darker colors indicate deep Earthquakes. The Catalogue is also expected to have a multidisciplinary use in a wide range of studies such as global seismicity assessment, tectonics, as well as the rapid determination of seismic hazard. Because of the large volume of digitized seismic travel‐time and amplitude data generated during this project, we expect the Catalogue to be useful in studies of the inner structure of the Earth as well as in nuclear monitoring research. This global catalog was also designed to serve as a reference to be used for calibration purposes by those compiling regional seismicity catalogs that contain events of much smaller magnitudes. This will guarantee that the catalogs prepared by other teams for different regions will contain comparable Earthquake locations and magnitude parameters, especially in border areas. The work on the Catalogue was funded by the GEM Foundation as part of the five Global Hazard Components and is a result of a 27‐month‐long project. This project was led by the ISC and performed by the team of international experts in accordance with the requirements of the Scientific Board of GEM and following recommendations of the International Association of Seismology and Physics of the Earth’s Interior (IASPEI) observers. Further, eight IT, administrative, and technical staff …
Antonio Villasenor - One of the best experts on this subject based on the ideXlab platform.
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isc gem global instrumental Earthquake Catalogue 1900 2009 i data collection from early instrumental seismological bulletins
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Domenico Di Giacomo, J S Harris, Antonio Villasenor, Dmitry A Storchak, Robert E Engdahl, William H K LeeAbstract:Abstract In order to produce a new global reference Earthquake Catalogue based on instrumental data covering the last 100+ years of global Earthquakes, we collected, digitized and processed an unprecedented amount of printed early instrumental seismological bulletins with fundamental parametric data for relocating and reassessing the magnitude of Earthquakes that occurred in the period between 1904 and 1970. This effort was necessary in order to produce an Earthquake Catalogue with locations and magnitudes as homogeneous as possible. The parametric data obtained and processed during this work fills a large gap in electronic bulletin data availability. This new dataset complements the data publicly available in the International Seismological Centre (ISC) Bulletin starting in 1964. With respect to the amplitude-period data necessary to re-compute magnitude, we searched through the global collection of printed bulletins stored at the ISC and entered relevant station parametric data into the database. As a result, over 110,000 surface and body-wave amplitude-period pairs for re-computing standard magnitudes M S and m b were added to the ISC database. To facilitate Earthquake relocation, different sources have been used to retrieve body-wave arrival times. These were entered into the database using optical character recognition methods (International Seismological Summary, 1918–1959) or manually (e.g., British Association for the Advancement of Science, 1913–1917). In total, ∼1,000,000 phase arrival times were added to the ISC database for large Earthquakes that occurred in the time interval 1904–1970. The selection of Earthquakes for which data was added depends on time period and magnitude: for the early years of last century (until 1917) only very large Earthquakes were selected for processing ( M ⩾ 7.5), whereas in the periods 1918–1959 and 1960–2009 the magnitude thresholds are 6.25 and 5.5, respectively. Such a selection was mainly dictated by limitations in time and funding. Although the newly available parametric data is only a subset of the station data available in the printed bulletins, its electronic availability will be important for any future study of Earthquakes that occurred during the early instrumental period.
-
the isc gem global instrumental Earthquake Catalogue 1900 2009 introduction
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Dmitry A Storchak, Domenico Di Giacomo, J S Harris, William H K Lee, E R Engdahl, Istvan Bondar, Peter Bormann, Antonio VillasenorAbstract:Abstract In this introductory article we give a general description of the ISC-GEM Global Instrumental Earthquake Catalogue (1900–2009). We also provide the background for four further articles that describe the effort in collecting and digitizing parametric Earthquake bulletin data as well as the methodologies developed to compute homogeneous Earthquake parameters. The result of the two and a half year project is a Catalogue of approximately 20,000 large Earthquakes covering 110 years with hypocentres and uncertainties computed using the same technique and velocity model. We show that the overall homogeneity of the main Earthquake parameters in the Catalogue was achieved despite changes in instrumentation and routine measurement practices concurrent with developments in instrumental seismology from almost a ground level to its current state. For each Earthquake, MW magnitude values and uncertainties were computed either based on available estimates of seismic moment or using new empirical relationships between MW, MS and mb. Further important results of this project include the electronic availability of a considerable volume of seismic wave arrival time and amplitude measurements from early instrumental printed station bulletins. These newly recovered amplitude measurements provided a basis for computation of many previously unavailable MS magnitudes with uncertainties. In this article we describe why such a Catalogue is required for a comprehensive assessment of global and regional seismic hazard. We also describe other potential uses of the Catalogue in many other fields of Earth Sciences. We discuss the Catalogue availability and lay out the plans of further development.
-
isc gem global instrumental Earthquake Catalogue 1900 2009 ii location and seismicity patterns
Physics of the Earth and Planetary Interiors, 2015Co-Authors: Istvan Bondar, J S Harris, Antonio Villasenor, Robert E Engdahl, Dmitry A StorchakAbstract:Abstract We present the final results of a two-year project sponsored by the Global Earthquake Model (GEM) Foundation. The ISC-GEM global Catalogue consists of some 19 thousand instrumentally recorded, moderate to large Earthquakes, spanning 110 years of seismicity. We relocated all events in the Catalogue using a two-tier approach. The EHB location methodology (Engdahl et al., 1998) was applied first to obtain improved hypocentres with special focus on the depth determination. The locations were further refined in the next step by fixing the depths to those from the EHB analysis and applying the new International Seismological Centre (ISC) location algorithm (Bondar and Storchak, 2011) that reduces location bias by accounting for correlated travel-time prediction error structure. To facilitate the relocation effort, some one million seismic P and S wave arrival-time data were added to the ISC database for the period between 1904 and 1970, either from original station bulletins in the ISC archive or by digitizing the scanned images of the International Seismological Summary (ISS) bulletin (Villasenor and Engdahl, 2005, 2007). Although no substantial amount of new phase data were acquired for the modern period (1964–2009), the number of phases used in the location has still increased by three millions, owing to fact that both the EHB and ISC locators use most well-recorded ak135 (Kennett et al., 1995) phases in the location. We show that the relocation effort yielded substantially improved locations, especially in the first half of the 20th century; we demonstrate significant improvements in focal depth estimates in subduction zones and other seismically active regions; and we show that the ISC-GEM Catalogue provides an improved view of 110 years of global seismicity of the Earth. The ISC-GEM Global Instrumental Earthquake Catalogue represents the final product of one of the ten global components in the GEM program, and is available to researchers at the ISC ( www.isc.ac.uk ) website.
-
public release of the isc gem global instrumental Earthquake Catalogue 1900 2009
Seismological Research Letters, 2013Co-Authors: Dmitry A Storchak, Domenico Di Giacomo, J S Harris, Antonio Villasenor, Robert E Engdahl, William H K Lee, Istvan Bondar, Peter BormannAbstract:The International Seismological Centre–Global Earthquake Model (ISC–GEM) Global Instrumental Earthquake Catalogue (1900–2009) is the result of a special effort to substantially extend and improve currently existing global catalogs to serve the requirements of specific user groups who assess and model seismic hazard and risk. The data from the ISC–GEM Catalogue would be used worldwide yet will prove absolutely essential in those regions where a high seismicity level strongly correlates with a high population density (Fig. 1). Figure 1. Earthquakes from the ISC–GEM Catalogue in Central and South America. Lighter colors indicate shallow Earthquakes and darker colors indicate deep Earthquakes. The Catalogue is also expected to have a multidisciplinary use in a wide range of studies such as global seismicity assessment, tectonics, as well as the rapid determination of seismic hazard. Because of the large volume of digitized seismic travel‐time and amplitude data generated during this project, we expect the Catalogue to be useful in studies of the inner structure of the Earth as well as in nuclear monitoring research. This global catalog was also designed to serve as a reference to be used for calibration purposes by those compiling regional seismicity catalogs that contain events of much smaller magnitudes. This will guarantee that the catalogs prepared by other teams for different regions will contain comparable Earthquake locations and magnitude parameters, especially in border areas. The work on the Catalogue was funded by the GEM Foundation as part of the five Global Hazard Components and is a result of a 27‐month‐long project. This project was led by the ISC and performed by the team of international experts in accordance with the requirements of the Scientific Board of GEM and following recommendations of the International Association of Seismology and Physics of the Earth’s Interior (IASPEI) observers. Further, eight IT, administrative, and technical staff …
