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Robert W Clayton - One of the best experts on this subject based on the ideXlab platform.
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seismicity and structure in central mexico evidence for a possible slab tear in the south Cocos Plate
Journal of Geophysical Research, 2014Co-Authors: Sara L Dougherty, Robert W ClaytonAbstract:The morphology of the transition from flat to normal subduction in eastern central Mexico is explored using intraslab earthquakes recorded by temporary and permanent regional seismic arrays. Observations of a sharp transition in slab dip near the abrupt end of the Trans-Mexican Volcanic Belt (TMVB) suggest a possible slab tear located within the subducted South Cocos Plate. The eastern lateral extent of a thin ultra-slow velocity layer (USL) imaged atop the Cocos slab in recent studies along the Meso America Subduction Experiment array is examined here using additional data. We find an end to this USL which is coincident with the western boundary of a zone of decreased seismicity and the end of the TMVB near the sharp transition in slab dip. Waveform modeling of the 2-D structure in this region using a finite difference algorithm provides constraints on the velocity and geometry of the slab's seismic structure and confirms the location of the USL. Analysis of intraslab seismicity patterns reveals clustering, sudden increase in depth, variable focal mechanism orientations and faulting types, and alignment of source mechanisms along the sharp transition in slab dip. The seismicity and structural evidence suggests a possible tear in the South Cocos slab. This potential tear, together with the tear along the Orozco Fracture Zone to the northwest, indicates a slab rollback mechanism in which separate slab segments move independently, allowing for mantle flow between the segments.
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seismic structure in central mexico implications for fragmentation of the subducted Cocos Plate
Journal of Geophysical Research, 2012Co-Authors: Sara L Dougherty, Robert W Clayton, Donald V HelmbergerAbstract:[1] The fine-scale seismic structure of the central Mexico subduction zone is studied using moderate-sized (M4-6) intraslab earthquakes. Regional waveforms from the Mapping the Rivera Subduction Zone (MARS) seismic array are complicated and contain detailed information about the subduction zone structure, including evidence of lateral heterogeneity. This waveform information is used to model the structure of the subducted Plates, particularly along the transition from flat to normal subduction, where recent studies have shown evidence for possible slab tearing along the eastern projection of the Orozco Fracture Zone (OFZ). The lateral extent of a thin ultra-slow velocity layer (USL) imaged atop the Cocos slab in recent studies along the Meso America Subduction Experiment array is examined here using MARS waveforms. We find an edge to this USL which is coincident with the western boundary of the projected OFZ region. Forward modeling of the 2D structure of the subducted Rivera and Cocos Plates using a finite difference algorithm provides constraints on the velocity and geometry of each slab’s seismic structure in this region and confirms the location of the USL edge. We propose that the Cocos slab is currently fragmenting into a North Cocos Plate and a South Cocos Plate along the projection of the OFZ, in agreement with observations of variable Cocos Plate motion on either side of the OFZ. This tearing event may be a young analogy to the 10 Ma Rivera-Cocos Plate boundary, and may be related to the slab rollback in central Mexico.
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seismic imaging of the Cocos Plate subduction zone system in central mexico
Geochemistry Geophysics Geosystems, 2012Co-Authors: Younghee Kim, Meghan S Miller, Frederick Pearce, Robert W ClaytonAbstract:Broadband data from the Meso-America Subduction Experiment (MASE) line in central Mexico were used to image the subducted Cocos Plate and the overriding continental lithosphere beneath central Mexico using a generalized radon transform based migration. Our images provide insight into the process of subducting relatively young oceanic lithosphere and its complex geometry beneath continental North America. The converted and reverberated phase image shows complete horizontal tectonic underplating of the Cocos oceanic lithosphere beneath the North American continental lithosphere, with a clear image of a very thin low-velocity oceanic crust (7–8 km) which dips at 15–20 degrees at Acapulco then flattens approximately 300 km from the Middle America Trench. Farther inland the slab then appears to abruptly change from nearly horizontal to a steeply dipping geometry of approximately 75 degrees underneath the Trans-Mexican Volcanic Belt (TMVB). Where the slab bends underneath the TMVB, the migrated image depicts the transition from subducted oceanic Moho to continental Moho at ∼230 km from the coast, neither of which were clearly resolved in previous seismic images. The deeper seismic structure beneath the TMVB shows a prominent negative discontinuity (fast-to-slow) at ∼65–75 km within the upper mantle. This feature, which spans horizontally beneath the arc (∼100 km), may delineate the top of a layer of ponded partial melt.
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geometry and seismic properties of the subducting Cocos Plate in central mexico
Journal of Geophysical Research, 2010Co-Authors: Robert W Clayton, Jennifer M JacksonAbstract:The geometry and properties of the interface of the Cocos Plate beneath central Mexico are determined from the receiver functions (RFs) utilizing data from the Meso America Subduction Experiment (MASE). The RF image shows that the subducting oceanic crust is shallowly dipping to the north at 15° for 80 km from Acapulco and then horizontally underPlates the continental crust for approximately 200 km to the Trans-Mexican Volcanic Belt (TMVB). The crustal image also shows that there is no continental root associated with the TMVB. The migrated image of the RFs shows that the slab is steeply dipping into the mantle at about 75° beneath the TMVB. Both the continental and oceanic Moho are clearly seen in both images, and modeling of the RF conversion amplitudes and timings of the underPlated features reveals a thin low-velocity zone between the Plate and the continental crust that appears to absorb nearly all of the strain between the upper Plate and the slab. By inverting RF amplitudes of the converted phases and their time separations, we produce detailed maps of the seismic properties of the upper and lower oceanic crust of the subducting Cocos Plate and its thickness. High Poisson's and Vp/Vs ratios due to anomalously low S wave velocity at the upper oceanic crust in the flat slab region may indicate the presence of water and hydrous minerals or high pore pressure. The evidence of high water content within the oceanic crust explains the flat subduction geometry without strong coupling of two Plates. This may also explain the nonvolcanic tremor activity and slow slip events occurring in the subducting Plate and the overlying crust.
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horizontal subduction and truncation of the Cocos Plate beneath central mexico
Geophysical Research Letters, 2008Co-Authors: Xyoli Perezcampos, Allen Husker, Paul M Davis, Robert W Clayton, A Iglesias, J F Pacheco, S K Singh, Vlad Constantin Manea, Michael GurnisAbstract:[1] Based on analysis of data from a trans-Mexico temporary broadband seismic network centered on Mexico City, we report that the subducting Cocos Plate beneath central Mexico is horizontal, and tectonically underPlates the base of the crust for a distance of 250 km from the trench. It is decoupled from the crust by a very thin low viscosity zone. The Plate plunges into the mantle near Mexico City but is truncated at a depth of 500 km, probably due to an E-W propagating tear in the Cocos slab. Unlike the shallow slab subduction in Peru and Chile, there is active volcanism along the Trans Mexican Volcanic Belt (TMVB) that lies much further inland than regions to either side where subduction dip is not horizontal. Geodynamical modeling indicates that a thin weak layer such as imaged by the seismic experiment can explain the flat subduction
Douglas S. Wilson - One of the best experts on this subject based on the ideXlab platform.
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Gravity lineaments of the Cocos Plate: Evidence for a thermal contraction crack origin
Geochemistry Geophysics Geosystems, 2011Co-Authors: Marie Helene Cormier, Kathleen D. Gans, Douglas S. WilsonAbstract:Lineaments in the gravity field with wavelengths of 100–200 km affect the south‐central Pacific. Because they align with absolute Plate motion, it has been proposed that they reflect small‐scale convection cells beneath the lithosphere that become elongated by basal shear. Alternatively, it was suggested that they reflect channelized flow of low viscosity material following the base of the lithosphere toward the East Pacific Rise, or that they result from lithospheric‐scale thermal contraction cracks. Here, we report about previously undetected gravity lineaments across the Cocos Plate. Similarly to the south‐central Pacific lineaments, the Cocos lineaments affect a Plate that is anomalously shallow, with seamounts aligning mostly within their troughs. However, the Cocos lineaments strike markedly oblique to absolute Plate motion and follow instead trajectories that are perpendicular to seafloor isochrons, a characteristic best explained by the thermal contraction crack model. The presence of steep scarps at the base of seamounts and the seismic imaging of faults striking perpendicular to isochrons further support this interpretation. Assuming that the slow subsidence rates of the south‐central Pacific and Cocos Plates reflect a warmer upper mantle, we propose that the associated thinner elastic Plates favor the formation of thermal contraction cracks. A thinner elastic Plate may also explain the pattern of ridge propagation in both areas. At large ridge offsets with a history of steady migration, the propagating segments have been those cutting into the shallower flanks, consistent with the concept that a warmer, thinner Plate is more easily cracked.
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fastest known spreading on the miocene Cocos pacific Plate boundary
Geophysical Research Letters, 1996Co-Authors: Douglas S. WilsonAbstract:New magnetic anomaly identifications for the central part of the Cocos Plate and the corresponding part of the Pacific Plate indicate a pulse of extremely rapid seafloor spreading in the middle Miocene, about 11–18 Ma, possibly beginning as early as 25 Ma. The spacing of anomalies 5A–5D indicates a full spreading rate for the southern Cocos-Pacific boundary of 180–210 mm/yr, depending on the choice of time scale. Relative to the maximum 0–3 Ma spreading rate of 152 mm/yr, this result significantly expands the upper limit of well documented rates.
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Fastest known spreading on the Miocene Cocos‐Pacific Plate Boundary
Geophysical Research Letters, 1996Co-Authors: Douglas S. WilsonAbstract:New magnetic anomaly identifications for the central part of the Cocos Plate and the corresponding part of the Pacific Plate indicate a pulse of extremely rapid seafloor spreading in the middle Miocene, about 11–18 Ma, possibly beginning as early as 25 Ma. The spacing of anomalies 5A–5D indicates a full spreading rate for the southern Cocos-Pacific boundary of 180–210 mm/yr, depending on the choice of time scale. Relative to the maximum 0–3 Ma spreading rate of 152 mm/yr, this result significantly expands the upper limit of well documented rates.
Paul M Davis - One of the best experts on this subject based on the ideXlab platform.
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Tomography and thermal state of the Cocos Plate subduction beneath Mexico City
Journal of Geophysical Research, 2009Co-Authors: Allen Husker, Paul M DavisAbstract:[1] The geometry and thermal state of the subducting Cocos Plate beneath Mexico City has been enigmatic because of the absence of a deep Wadati-Benioff zone. We present a tomographic image of the slab based on inversion of 8869 teleseismic P wave travel times measured on a portable broadband seismic network. The images combined with receiver function analysis show that the slab runs flat from the coast to near Mexico City, where it dives into the mantle just before the Trans-Mexican Volcanic Belt with a dip of ∼75°. It continues down to a depth of ∼500 km at a distance of 400 km from the trench, where the tomography reveals that the dipping portion ends. As well as standard block tomography, we invert the travel time residuals for the parameters of a thermal slab model and find a slab thickness of 40 km that is consistent with the (15 Ma) age of the Cocos Plate. The combination of a young hot Plate and truncation at depth can explain the lack of deep seismicity due to high temperatures and lower negative buoyancy compared with an older, thicker, nontruncated Plate.
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horizontal subduction and truncation of the Cocos Plate beneath central mexico
Geophysical Research Letters, 2008Co-Authors: Xyoli Perezcampos, Allen Husker, Paul M Davis, Robert W Clayton, A Iglesias, J F Pacheco, S K Singh, Vlad Constantin Manea, Michael GurnisAbstract:[1] Based on analysis of data from a trans-Mexico temporary broadband seismic network centered on Mexico City, we report that the subducting Cocos Plate beneath central Mexico is horizontal, and tectonically underPlates the base of the crust for a distance of 250 km from the trench. It is decoupled from the crust by a very thin low viscosity zone. The Plate plunges into the mantle near Mexico City but is truncated at a depth of 500 km, probably due to an E-W propagating tear in the Cocos slab. Unlike the shallow slab subduction in Peru and Chile, there is active volcanism along the Trans Mexican Volcanic Belt (TMVB) that lies much further inland than regions to either side where subduction dip is not horizontal. Geodynamical modeling indicates that a thin weak layer such as imaged by the seismic experiment can explain the flat subduction
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seismic tomography of the Cocos Plate
Center for Embedded Network Sensing, 2006Co-Authors: Allen Husker, Paul M DavisAbstract:The position of the subducting Cocos Plate beneath Mexico is unknown from the Trans-Mexican Volcanic Belt (TMVB) northward. Geochemical analysis suggests that there may be a slab tear causing mafic volcanism along the northern edge of the (TMVB). An array of 100 seismometers at 5 km spacing is currently installed in Mexico by the MesoAmerican Seismic Experiment (MASE) in conjunction with the Center for Embedded Networked Sensing (CENS) at UCLA, the Universidad Nacional Autonoma de Mexico (UNAM), and the California Institute of Technology (CIS). The data from this array is used to develop P and S wave tomographies to locate the slab. Beneath the MASE line the Cocos Plate dips from the trench to a ~ 50 km depth. It is almost subhorizontal between 110 km to 275 km from the trench at a ~50 km depth. Then it continues to dip at a near constant angle.
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seismic tomography of the Cocos Plate
AGUFM, 2006Co-Authors: Allen Husker, Paul M DavisAbstract:Author(s): Husker, Allen; Davis, Paul | Abstract: The position of the subducting Cocos Plate beneath Mexico is unknown from the Trans-Mexican Volcanic Belt (TMVB) northward. Geochemical analysis suggests that there may be a slab tear causing mafic volcanism along the northern edge of the (TMVB). An array of 100 seismometers at 5 km spacing is currently installed in Mexico by the MesoAmerican Seismic Experiment (MASE) in conjunction with the Center for Embedded Networked Sensing (CENS) at UCLA, the Universidad Nacional Autonoma de Mexico (UNAM), and the California Institute of Technology (CIS). The data from this array is used to develop P and S wave tomographies to locate the slab. Beneath the MASE line the Cocos Plate dips from the trench to a ~ 50 km depth. It is almost subhorizontal between 110 km to 275 km from the trench at a ~50 km depth. Then it continues to dip at a near constant angle.
Gerardo Suarez - One of the best experts on this subject based on the ideXlab platform.
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Large earthquakes in the Tehuantepec subduction zone: evidence of a locked Plate interface and large-scale deformation of the slab
Journal of Seismology, 2020Co-Authors: Gerardo SuarezAbstract:The Tehuantepec subduction zone was identified as a seismic gap by several authors. The presence of three large earthquakes at the turn of the twentieth century, in temporal and spatial proximity, poses questions on the extent of the seismic gap and on the type of tectonic deformation in this region. On 19 April 1902, a large earthquake occurred in Guatemala. The macroseismic data and recent relocations suggest that it is not a subduction event but an intraPlate earthquake within the subducted Cocos Plate. The recent relocations and the macroseismic data of the 23 September 1902 earthquake, which is frequently interpreted as an interPlate subduction event, show that it is an intermediate-depth earthquake located inland in central Mexico. The 14 January 1903 earthquake, located in the Gulf of Tehuantepec, may be interpreted as an intraPlate event, similar to the 8 September 2017 earthquake ( M _w 8.2) or a subduction earthquake. Thus, there is no clear evidence of large subduction earthquakes ( M _w > 7) in Tehuantepec at least in the last 250 years. Geodetic data suggest that the subduction zone is highly coupled and, therefore, a considerable amount of Plate motion has not been released. The length of the presumed seismic gap is equivalent to a M _w ~ 8.5 earthquake. In contrast, the September 1902 ( M _w 7.8), 1903 ( M _w 7.4), 1931 ( M _w 7.8), 1999 ( M _w 7.5) and the great 8 September 2017 events ( M _w 8.2) are all down-dip tensional earthquakes in the slab, reflecting a complex state of stress in the downgoing Cocos Plate. These frequent and large tensional earthquakes may reflect a large-scale deformation of the slab that locked at the Plate interface is under tensional stress under its own gravitational weight. As a result, seismic hazard in the Isthmus of Tehuantepec stems from both subduction and intraPlate earthquakes.
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large scale lithospheric detachment of the downgoing Cocos Plate the 8 september 2017 earthquake mw 8 2
Earth and Planetary Science Letters, 2019Co-Authors: Gerardo Suarez, Arturo Iglesias, Miguel A Santoyo, Vala Hjorleifsdottir, Carlos Villafuerte, V M CruzatienzaAbstract:Abstract On 8 September 2017, a great earthquake ( M w 8.2) took place in the Mexican subduction zone in the Tehuantepec gap, where no large subduction earthquakes have taken place since 1902. However, the 8 September earthquake did not occur on the contact between the Cocos and North American Plates. The centroidal hypocentral depths reported by different agencies, including the National Seismological Service, range from 45 to 47.4 km, placing it immediately beneath the down-dip limit of the interPlate locked zone. The source mechanism reflects down-dip tensional faulting. The inversion of the fault process shows a rupture that initiated at the bottom of the lithosphere and propagated upward, breaking through the entire subducted lithosphere. An unusually long, complex and copious aftershock sequence followed the main event. The relocated aftershocks, in the first 20 days following the main event, delineate a 160-km-long fault, sub-parallel to the oceanic trench, immediately beneath the interPlate contact. The aftershocks also concentrate in secondary intraslab faults ∼50 km down-dip from the mainshock rupture, revealing that pervasive tensional stresses are present within the subducted Plate. This deformation pattern suggests a large-scale tensional regime in the slab, apparently induced by its own gravitational weight that pulls it away from the strongly coupled interPlate contact. Other large intraPlate earthquakes in the vicinity, in 1931 ( M w 7.8) and 1999 ( M w 7.5), also reflect this detachment of the downgoing Cocos Plate that sinks into the mantle under its own gravitational weight. The slab detachment suggests that the up-dip segment of the Plate interface near the Isthmus of Tehuantepec is locked and possibly primed for a megathrust earthquake, such as the M w 8.6 that took place in 1787, on an adjacent segment of the Mexican subduction zone.
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the 11 december 1995 earthquake mw 6 4 implications for the present day relative motion on the rivera Cocos Plate boundary
Geophysical Research Letters, 1999Co-Authors: Gerardo Suarez, David Escobedo, W Bandy, J F PachecoAbstract:The 11 December, 1995 earthquake is the largest and best constrained instrumentally recorded event which has occurred on the Rivera-Cocos Plate boundary. The reported focal mechanism for this event indicates almost pure strike-slip faulting with nodal planes oriented north-south and east-west. A visual inspection shows that the seismograms recorded world-wide strongly suggest a directivity effect indicative of a rupture propagating eastward from the epicenter. This observation is confirmed by a directivity analysis which shows a sharp reduction in the difference between observed and synthetic seismograms when the rupture direction is at an azimuth of approximately 90°. These results indicate that the east-west trending nodal plane of the earthquake of 11 December, 1995 is the actual fault plane. Considering that this is the largest instrumentally recorded earthquake in the region, it strongly suggests that the relative motion of the Rivera Plate with respect to the Cocos Plate takes place along east-west oriented faults, and that the sense of motion is right-lateral, strike-slip.
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steep subduction geometry of the rivera Plate beneath the jalisco block in western mexico
Geophysical Research Letters, 1993Co-Authors: Mario Pardo, Gerardo SuarezAbstract:The morphology of the Rivera Plate subducted beneath the Jalisco block in western Mexico is determined from accurately located hypocenters of locally recorded microearthquakes, and from earthquakes with magnitude mb≥4.5 recorded at teleseismic distances. The hypocenters of these latter earthquakes are relocated, and for five of them the focal depth is constrained by the inversion of long-period body waves. The Wadati-Benioff zone inferred from these data indicates a steep subduction of the Rivera Plate that resembles the geometry of subduction of the Cocos Plate beneath Central America. It is, however, very different from the shallower and almost subhorizontal subduction of the Cocos Plate observed in southern Mexico, southeast of this region. The Rivera Plate is comparable to the Juan de Fuca Plate in terms of the small areal extent, young seafloor age, low relative velocity, and low teleseismic activity in the subduction zone. This study shows that the dip of both the Juan de Fuca and Rivera Plates are similar once they are decoupled from the overriding continental crust. The downgoing Rivera Plate initially starts with a dip of ∼10° down to a depth of 20 km and then increases gradually to a constant dip of ∼50° below a depth of 40 km. Intermediate-depth seismicity is low in this zone associated with the subduction of the slow (2 cm/yr) and young (9 m.y.) Rivera Plate. The maximum depth extent of earthquakes observed in the Rivera subduction zone is about 130 km. The andesitic, calc-alkaline Colima volcano appears to be directly related to the subduction of the Rivera Plate. To the NW of this volcano, the observed Quaternary volcanism in the Jalisco block, which is parallel to the trench, may also be explained by the subduction of the Rivera Plate.
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geometry and state of stress of the downgoing Cocos Plate in the isthmus of tehuantepec mexico
Geophysical Research Letters, 1992Co-Authors: L Ponce, Roland Gaulon, Gerardo Suarez, Elias LomasAbstract:The seismicity in the Isthmus of Tehuantepec, Mexico is anomalously active compared with other parts of the Middle American subduction zone. The results of a microearthquake study conducted in this region show that the slab changes dip from an almost subhorizontal geometry west of longitude 96° W, to a dip of about 45° to 50° to the east of this longitude. The change in dip occurs gradually in a broad flexure of the subducting slab that takes place over 150 km. This geometry of the slab is reminiscent of that in southern Peru; the change in dip, however, takes place more gently in Tehuantepec. In addition to the change in the dip of the subducted Cocos Plate, a rapid increase is observed in the maximum depth extent of the subducted slab. In the region of subhorizontal subduction, focal depths are consistently shallower than about 80 km, whereas earthquakes as deep as 200 km are found where the subducted slab dips at a steeper angle. Both the change in the dip of the slab and of the maximum depth of intermediate-depth earthquakes appear to correlate with the presence of the Tehuantepec Fracture Zone which separates two distinct provinces of the oceanic Cocos Plate. The age and the crustal thickness of the Cocos Plate increase to the southeast of the Tehuantepec Fracture Zone relative to its northwestern counterpart. In Tehuantepec, the dip and maximum depth of the subducted slab appears to be correlated with the age of the oceanic Plate, as has been observed in other subduction zones of the world.
Allen Husker - One of the best experts on this subject based on the ideXlab platform.
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Tomography and thermal state of the Cocos Plate subduction beneath Mexico City
Journal of Geophysical Research, 2009Co-Authors: Allen Husker, Paul M DavisAbstract:[1] The geometry and thermal state of the subducting Cocos Plate beneath Mexico City has been enigmatic because of the absence of a deep Wadati-Benioff zone. We present a tomographic image of the slab based on inversion of 8869 teleseismic P wave travel times measured on a portable broadband seismic network. The images combined with receiver function analysis show that the slab runs flat from the coast to near Mexico City, where it dives into the mantle just before the Trans-Mexican Volcanic Belt with a dip of ∼75°. It continues down to a depth of ∼500 km at a distance of 400 km from the trench, where the tomography reveals that the dipping portion ends. As well as standard block tomography, we invert the travel time residuals for the parameters of a thermal slab model and find a slab thickness of 40 km that is consistent with the (15 Ma) age of the Cocos Plate. The combination of a young hot Plate and truncation at depth can explain the lack of deep seismicity due to high temperatures and lower negative buoyancy compared with an older, thicker, nontruncated Plate.
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horizontal subduction and truncation of the Cocos Plate beneath central mexico
Geophysical Research Letters, 2008Co-Authors: Xyoli Perezcampos, Allen Husker, Paul M Davis, Robert W Clayton, A Iglesias, J F Pacheco, S K Singh, Vlad Constantin Manea, Michael GurnisAbstract:[1] Based on analysis of data from a trans-Mexico temporary broadband seismic network centered on Mexico City, we report that the subducting Cocos Plate beneath central Mexico is horizontal, and tectonically underPlates the base of the crust for a distance of 250 km from the trench. It is decoupled from the crust by a very thin low viscosity zone. The Plate plunges into the mantle near Mexico City but is truncated at a depth of 500 km, probably due to an E-W propagating tear in the Cocos slab. Unlike the shallow slab subduction in Peru and Chile, there is active volcanism along the Trans Mexican Volcanic Belt (TMVB) that lies much further inland than regions to either side where subduction dip is not horizontal. Geodynamical modeling indicates that a thin weak layer such as imaged by the seismic experiment can explain the flat subduction
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seismic tomography of the Cocos Plate
Center for Embedded Network Sensing, 2006Co-Authors: Allen Husker, Paul M DavisAbstract:The position of the subducting Cocos Plate beneath Mexico is unknown from the Trans-Mexican Volcanic Belt (TMVB) northward. Geochemical analysis suggests that there may be a slab tear causing mafic volcanism along the northern edge of the (TMVB). An array of 100 seismometers at 5 km spacing is currently installed in Mexico by the MesoAmerican Seismic Experiment (MASE) in conjunction with the Center for Embedded Networked Sensing (CENS) at UCLA, the Universidad Nacional Autonoma de Mexico (UNAM), and the California Institute of Technology (CIS). The data from this array is used to develop P and S wave tomographies to locate the slab. Beneath the MASE line the Cocos Plate dips from the trench to a ~ 50 km depth. It is almost subhorizontal between 110 km to 275 km from the trench at a ~50 km depth. Then it continues to dip at a near constant angle.
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seismic tomography of the Cocos Plate
AGUFM, 2006Co-Authors: Allen Husker, Paul M DavisAbstract:Author(s): Husker, Allen; Davis, Paul | Abstract: The position of the subducting Cocos Plate beneath Mexico is unknown from the Trans-Mexican Volcanic Belt (TMVB) northward. Geochemical analysis suggests that there may be a slab tear causing mafic volcanism along the northern edge of the (TMVB). An array of 100 seismometers at 5 km spacing is currently installed in Mexico by the MesoAmerican Seismic Experiment (MASE) in conjunction with the Center for Embedded Networked Sensing (CENS) at UCLA, the Universidad Nacional Autonoma de Mexico (UNAM), and the California Institute of Technology (CIS). The data from this array is used to develop P and S wave tomographies to locate the slab. Beneath the MASE line the Cocos Plate dips from the trench to a ~ 50 km depth. It is almost subhorizontal between 110 km to 275 km from the trench at a ~50 km depth. Then it continues to dip at a near constant angle.