The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Dinghui Yang - One of the best experts on this subject based on the ideXlab platform.
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The auxiliary function method for waveform based Earthquake location
Journal of Computational Physics, 2020Co-Authors: Jing Chen, Hao Jing, Ping Tong, Dinghui YangAbstract:Abstract This paper introduces the auxiliary function method, a novel, fast and simple approach for waveform based Earthquake location. From any initial Hypocenter and origin time, we can construct the auxiliary function, whose zero set contains the real Earthquake Hypocenter and the origin time. This translates the Earthquake location problem into the problem of searching the common zeros of the auxiliary functions. The computational cost of constructing the auxiliary functions is close to the cost of one single iteration of the traditional iterative method. And the cost of searching the common zeros of the auxiliary functions is almost negligible. Thus, the overall cost of this new method is significantly less than that of the iterative methods. Moreover, there is only one common zero point of the auxiliary functions in most practical situations. This means that the new method only requires one round of calculation to obtain an accurate Earthquake Hypocenter and origin time from arbitrary initial values. According to our numerical tests, even for large data noise, the method can still achieve good location results.
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The quadratic Wasserstein metric for Earthquake location
Journal of Computational Physics, 2018Co-Authors: Jing Chen, Yifan Chen, Dinghui YangAbstract:Abstract In Engquist et al. (2016) [8] , the Wasserstein metric was successfully introduced to the full waveform inversion. We apply this method to the Earthquake location problem. For this problem, the seismic stations are far from each other. Thus, the trace by trace comparison (Yang et al. [47] ) is a natural way to compare the Earthquake signals. Under this framework, we have derived a concise analytic expression of the Frechet gradient of the Wasserstein metric, which leads to a simple and efficient implementation of the adjoint method. We square and normalize the Earthquake signals for comparison so that the convexity of the misfit function with respect to Earthquake Hypocenter and origin time can be realized and observed numerically. To reduce the impact of noise, which does not offset each other after the signals are squared, a new control parameter is introduced. Finally, the LMF (Levenberg–Marquardt–Fletcher) method is applied to solve the resulted optimization problem. According to the numerical experiments, only a few iterations are required to converge to the real Earthquake Hypocenter and origin time. Even for data with noise, we can obtain reasonable and convergent numerical results.
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The auxiliary function method for waveform based Earthquake location
arXiv: Numerical Analysis, 2017Co-Authors: Jing Chen, Hao Jing, Ping Tong, Dinghui YangAbstract:This paper introduces the auxiliary function method (AFM), a novel, fast and simple approach for waveform based Earthquake location. From any initial Hypocenter and origin time, we can construct the auxiliary function, whose zero set contains the real Earthquake Hypocenter and the origin time. In most of situations, there are very few elements in this set. The overall computational cost of the AFM is significantly less than that of the iterative methods. According to our numerical tests, even for large noise, the method can still achieve good location results. These allow us to determine the Earthquake Hypocenter and the origin time extremely fast and accurate.
Jing Chen - One of the best experts on this subject based on the ideXlab platform.
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The auxiliary function method for waveform based Earthquake location
Journal of Computational Physics, 2020Co-Authors: Jing Chen, Hao Jing, Ping Tong, Dinghui YangAbstract:Abstract This paper introduces the auxiliary function method, a novel, fast and simple approach for waveform based Earthquake location. From any initial Hypocenter and origin time, we can construct the auxiliary function, whose zero set contains the real Earthquake Hypocenter and the origin time. This translates the Earthquake location problem into the problem of searching the common zeros of the auxiliary functions. The computational cost of constructing the auxiliary functions is close to the cost of one single iteration of the traditional iterative method. And the cost of searching the common zeros of the auxiliary functions is almost negligible. Thus, the overall cost of this new method is significantly less than that of the iterative methods. Moreover, there is only one common zero point of the auxiliary functions in most practical situations. This means that the new method only requires one round of calculation to obtain an accurate Earthquake Hypocenter and origin time from arbitrary initial values. According to our numerical tests, even for large data noise, the method can still achieve good location results.
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The quadratic Wasserstein metric for Earthquake location
Journal of Computational Physics, 2018Co-Authors: Jing Chen, Yifan Chen, Dinghui YangAbstract:Abstract In Engquist et al. (2016) [8] , the Wasserstein metric was successfully introduced to the full waveform inversion. We apply this method to the Earthquake location problem. For this problem, the seismic stations are far from each other. Thus, the trace by trace comparison (Yang et al. [47] ) is a natural way to compare the Earthquake signals. Under this framework, we have derived a concise analytic expression of the Frechet gradient of the Wasserstein metric, which leads to a simple and efficient implementation of the adjoint method. We square and normalize the Earthquake signals for comparison so that the convexity of the misfit function with respect to Earthquake Hypocenter and origin time can be realized and observed numerically. To reduce the impact of noise, which does not offset each other after the signals are squared, a new control parameter is introduced. Finally, the LMF (Levenberg–Marquardt–Fletcher) method is applied to solve the resulted optimization problem. According to the numerical experiments, only a few iterations are required to converge to the real Earthquake Hypocenter and origin time. Even for data with noise, we can obtain reasonable and convergent numerical results.
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The auxiliary function method for waveform based Earthquake location
arXiv: Numerical Analysis, 2017Co-Authors: Jing Chen, Hao Jing, Ping Tong, Dinghui YangAbstract:This paper introduces the auxiliary function method (AFM), a novel, fast and simple approach for waveform based Earthquake location. From any initial Hypocenter and origin time, we can construct the auxiliary function, whose zero set contains the real Earthquake Hypocenter and the origin time. In most of situations, there are very few elements in this set. The overall computational cost of the AFM is significantly less than that of the iterative methods. According to our numerical tests, even for large noise, the method can still achieve good location results. These allow us to determine the Earthquake Hypocenter and the origin time extremely fast and accurate.
Andri Dian Nugraha - One of the best experts on this subject based on the ideXlab platform.
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identification of active faults in west java indonesia based on Earthquake Hypocenter determination relocation and focal mechanism analysis
Geoscience Letters, 2018Co-Authors: Pepen Supendi, Andri Dian Nugraha, Nanang T Puspito, Sri Widiyantoro, Daryono DaryonoAbstract:We determined Earthquake locations through re-picking of P- and S-wave arrival times recorded by BMKG network. Earthquake locations were determined using Hypoellipse code that employs a single event determination method. We then relocated the events using Hypocenter double-difference method. We also conducted focal mechanism analysis to estimate the type of fault slip. The results indicate improved Hypocenter locations, where patterns of seismicity in West Java were delineated clearly. There are several clusters of Earthquakes at depths ≤ 30 km, which are probably related to the Cimandiri, Lembang, and Baribis faults. In addition, there is another cluster in Garut trending southwest-northeast, which is possibly related to a local fault. Histograms of travel-time residuals depict good results, in which travel-time residuals are mostly close to zero. Source mechanism throughout the Lembang fault indicates a left-lateral strike slip in agreement with previous studies. The Cimandiri fault also shows a left-lateral slip, but in the south it shows a thrust fault mechanism. While the source mechanisms of the western part of the Baribis fault indicate a thrust fault and the cluster of events in Garut shows a right-lateral slip if they are related to a local fault.
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Hypocenter Determination Using a Non-Linear Method for Events in West Java, Indonesia: A Preliminary Result
IOP Conference Series: Earth and Environmental Science, 2017Co-Authors: Shindy Rosalia, Pepen Supendi, Andri Dian Nugraha, Sri Widiyantoro, Hasbi Ash Shiddiqi, WandonoAbstract:West Java, part of the Sunda Arc, has relatively high seismicity due to subduction activity and faulting. The first step of tomography study in order to infer the geometry of the structure beneath West Java is to conduct precise Earthquake Hypocenter determination. In this study, we used Earthquake waveform data taken from the regional Meteorological, Climatological, Geophysical Agency (BMKG) network from South Sumatra to central Java. We have repicked P and S arrival times from about 800 events in the period from April 2009 to December 2015. We selected the events which have azimuthal gap < 210° and phase more than 8. The non-linear method employed in this study used the oct-tree sampling algorithm from NonLinLoc program to determine the Earthquake Hypocenters. The Hypocenter location results give better clustering Earthquakes which are correlated well with geological structure in the study region. We also compared our results with BMKG catalog data and found that the average Hypocenter location difference is about 12 km in latitude direction, 9.5 km in longitude direction, and the average focal depth difference is about 19.5 km. For future studies, we will conduct tomographic imaging to invert 3-D seismic velocity structure beneath the western part of Java.
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Relocation of volcano-tectonic Earthquake Hypocenter at Mt. Sinabung using double difference method
2017Co-Authors: Ulvienin Harlianti, Andri Dian Nugraha, Novianti IndrastutiAbstract:Sinabung is one of the active volcanoes in Indonesia that located in Karo, North Sumatra. Before the eruption in August 2010, this mountain is type-B volcano and then it change to type A volcano. Since the eruption in 2010, volcanic activity still continue and hasn’t show any signs of stopping yet. Due to volcanic activity, it causes an Earthquake in the body of the mountain. The type of Earthquakes that is recorded at Sinabung Mountain station are deep volcanic (VT-A), shallow volcanic (VT-B), tremors Earthquake, bellows Earthquake, low-frequency, high-frequency, regional tectonic Earthquake, local tectonic Earthquakes, eruptions and Earthquakes. VT-A and VT-B Earthquakes are associated with the magma movement process. This study reform 1D velocity model in Sinabung Mountain and relocate the Hypocenter using Double Difference (DD) method for the Earthquake data from July to December 2013. The purpose of Hypocenter relocation is to get the Earthquake position accurately so it can be interpreted better. Th...
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Preliminary result of Earthquake Hypocenter determination using hypoellipse around western Java region
2016Co-Authors: Pepen Supendi, Andri Dian NugrahaAbstract:West Java region is located in high seismicity and active tectonic setting region influenced by subducting Indo-Australian plate beneath Eurasia plate. There are several on land active faults namely Cimandiri fault, Lembang fault, and Baribis fault in the region. MCGA Earthquake data catalog from 2009 to 2014 shows the Earthquakes were located not only around active faults but also relatively far away from the active faults in West Java region. In this study, we determined the Earthquake location through re-picking of P-and S-wave arrival times recording by MCGA network. Earthquake location was determined by using Hypoellipse code that employs a single event determination method. We then relocated the events using Hypocenter double-difference method. We also have been conducting focal mechanism analysis to estimate the type of fault slip. Our preliminary results show generally the epicenter location were distributed around the on land active fault which have the focus depth less than 30 km. For ongoing an...
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micro Earthquake signal analysis and Hypocenter determination around lokon volcano complex
4TH INTERNATIONAL SYMPOSIUM ON EARTHQUAKE AND DISASTER MITIGATION 2014 (ISEDM 2014), 2015Co-Authors: Rizky Firmansyah, Andri Dian NugrahaAbstract:Mount Lokon is one of five active volcanoes which is located in the North Sulawesi region. Since June 26th, 2011, standby alert set by the Center for Volcanology and Geological Hazard Mitigation (CVGHM) for this mountain. The Mount Lokon volcano erupted on July 4th, 2011 and still continuously erupted until August 28th, 2011. Due to its high seismic activity, this study is focused to analysis of micro-Earthquake signal and determine the micro-Earthquake Hypocenter location around the complex area of Lokon-Empung Volcano before eruption phase in 2011 (time periods of January, 2009 up to March, 2010). Determination of the Hypocenter location was conducted with Geiger Adaptive Damping (GAD) method. We used initial model from previous study in Volcan de Colima, Mexico. The reason behind the model selection was based on the same characteristics that shared between Mount Lokon and Colima including andesitic stratovolcano and small-plinian explosions volcanian types. In this study, a picking events was limited t...
Hsien-hsiang Hsieh - One of the best experts on this subject based on the ideXlab platform.
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The deep structure of south-central Taiwan illuminated by seismic tomography and Earthquake Hypocenter data
Tectonophysics, 2016Co-Authors: Giovanni Camanni, Joaquina Alvarez-marrón, Dennis Brown, C. Ayala, Hsien-hsiang HsiehAbstract:Abstract The Taiwan mountain belt is generally thought to develop above a through-going basal thrust confined to within the sedimentary cover of the Eurasian continental margin. Surface geology, magnetotelluric, Earthquake Hypocenter, and seismic tomography data suggest, however, that crustal levels below this basal thrust are also currently being involved in the deformation. Here, we combine seismic tomography and Earthquake Hypocenter data to investigate the deformation that is taking place at depth beneath south-central Taiwan. In this paper, we define the basement as any pre-Eocene rifting rocks, and use a P-wave velocity of 5.2 km/s as a reference for the interface between these rocks and their sedimentary cover. We found that beneath the Coastal Plain and the Western Foothills clustering of Hypocenters near the basement-cover interface suggests that this interface is acting as a detachment. This detachment is located below the basal thrust proposed from surface geology for this part of the mountain belt. Inherited basement faults appear to determine the geometry of this detachment, and their inversion in the Alishan area result in the development of a basement uplift and a lateral structure in the thrust system above them. However, across the Shuilikeng and the Chaochou faults, Earthquake Hypocenters define steeply dipping clusters that extend to greater than 20 km depth, above which higher velocity basement rocks are uplifted beneath the Hsuehshan and Central ranges. We interpret these clusters to form a deeply penetrating, east-dipping ramp that joins westward with the detachment at the basement-cover interface. It is not possible to define a basal thrust to the east, beneath the Central Range.
Wim Spakman - One of the best experts on this subject based on the ideXlab platform.
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reconstructing subducted oceanic lithosphere by reverse engineering slab geometries the northern philippine sea plate
Tectonics, 2017Co-Authors: Jonathan M Pownall, Gordon S Lister, Wim SpakmanAbstract:Subducting slabs commonly acquire complex geometries from the migration of subduction trenches, slab-mantle interaction, slab tearing, and collision of slabs at depth. Although it is possible to construct three-dimensional models of subducted slabs using Earthquake Hypocenter locations and tomographic models, it is often not possible to rigorously test their accuracy. Here we present a methodology for performing such a test, by “reverse-engineering” the presubduction configuration of a slab of oceanic lithosphere from interpretations of its present-day morphology. We illustrate our approach for the Ryukyu and Shikoku slabs, northwest Philippine Sea, having simulated them as viscoelastic sheets that we unfolded and “floated” to the surface. The net strain distribution of the floated mesh indicated which parts of the original slab model were geometrically viable (minimal net strain) and which parts of the mesh required additional tears and/or zones of localized ductile extension to have enabled the slab to deform during subduction. In the instance of the Ryukyu and Shikoku slabs, the Palau-Kyushu and Gagua ridges are shown to have both acted as planes of weakness that broke into major vertical slab tears. These subducted ridges are connected by a trench-parallel tear that represented the former contact between the Huatung and West Philippine Basins. The fossil spreading center of the Shikoku Basin formed a separate slab window upon subduction along the Nankai Trough. The methodology presented herein is a powerful tool to evaluate complex slab morphologies, infer the locations of slab tears, and therefore reconstruct intricate configurations of subducted oceanic lithosphere.
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geodynamics of flat subduction seismicity and tomographic constraints from the andean margin
Tectonics, 2000Co-Authors: Marcandre Gutscher, Wim Spakman, Harmen Bijwaard, Robert E EngdahlAbstract:The cause and geodynamic impact of fiat subduction are investigated. First, the 1500 km long Peru fiat slab segment is examined. Earthquake Hypocenter data image two morphologic highs in the subducting Nazca Plate which correlate with the posi- tions of subducted oceanic plateaus. Travel time tomo- graphic images confirm the three-dimensional slab ge- ometry and suggest a lithospheric tear may bound the NW edge of the fiat slab segment, with possible slab de- tachment occurring down dip as well. Other fiat slab re- gions worldwide are discussed: central Chile, Ecuador, NW Colombia, Costa Rica, Mexico, southern Alaska, SW Japan, and western New Guinea. Flat subduction is shown to be a widespread phenomenon, occuring in 10% of modern convergent margins. in nearly all these cases, as a spatial and temporal correlation is observed between subducting oceanic plateaus and fiat subduc- tion, we conclude that fiat subduction is caused pri- marily by (1) the buoyancy of thickened oceanic crust of moderate to young age and (2) a delay in the basalt to eclogite transition due to the cool thermal structure of two overlapping lithospheres. A statistical analysis of seismicity along the entire length of the Andes demon- strates that seismic energy release in the upper plate at a distance of 250-800 km from the trench is on aver- age 3-5 times greater above fiat slab segments than for adjacent steep slab segments. We propose this is due to higher interplate coupling and the cold, strong rhe- ology of the overriding lithosphere which thus enables stress and deformation to be transmitted hundreds of kilometers into the heart of the upper plate.
