scholarly journals A possible effect of an intermediate depth intraslab earthquake on seismic cycles of interplate earthquakes at a subduction zone

2004 ◽  
Vol 56 (6) ◽  
pp. 553-561 ◽  
Author(s):  
Naoyuki Kato
Keyword(s):  
Subduction Zone ◽  
Intermediate Depth ◽  
Intraslab Earthquake ◽  
Seismic Cycles ◽  
Interplate Earthquakes

Long-Term Interactions Between Intermediate Depth and Shallow Seismicity in North Chile Subduction Zone

2017 ◽  
Vol 44 (18) ◽  
pp. 9283-9292 ◽  
Author(s):  
Jorge Jara ◽  
Anne Socquet ◽  
David Marsan ◽  
Michel Bouchon
Keyword(s):  
Subduction Zone ◽  
Intermediate Depth

Improving Focal Mechanisms for Earthquakes in Taiwan Strait and Ryukyu Subduction Zone with Broadband Waveforms of Combined Networks

2020 ◽  
Author(s):  
Chieh-Chen Lee ◽  
Tai-Lin Tseng ◽  
Pei-Ru Jian
Keyword(s):  
Subduction Zone ◽  
Taiwan Strait ◽  
Focal Mechanisms ◽  
Passive Margin ◽  
Moho Depth ◽  
Offshore Area ◽  
Intermediate Depth ◽  
Velocity Models ◽  
Taiwan Shoal ◽  
Oblique Convergence

<p>  Taiwan region is a seismically active region formed by the oblique convergence between Philippine Sea Plate and Eurasia Plate. Focal mechanisms of most small-moderate sized earthquakes can be well constrained by the local seismic array, except for those occurred offshore Taiwan where azimuthal coverage is limited. To better understand the tectonic structures, it is desirable to improve the focal mechanisms using better located hypocenters, reasonable velocity models, and the best available stations. In this study we focus on the shallow earthquakes in Taiwan Strait and the intermediate-depth earthquakes in southernmost Ryukyu. Both regions are less explored but large historic events had been reported.</p><p>  For earthquakes in Taiwan Strait, we systematically studied earthquakes from 1996 to 2019, including the M<sub>w</sub>5.7 Taiwan Shoal sequence happened on 2018/11/25. A total of 22 new moment tensors (MTs) were resolved in the passive margin by combining Fujian and Taiwan seismic networks from either side of the strait. For events closer to Fujian, China, the velocity model with Moho depth of 35 km yields overall lower compensated linear vector dipole (CLVD) and acceptable misfit values; while as a 40 km thick crust is better for events closer to or on the shore of Taiwan. This Moho variation under the Taiwan Strait, although subtle, agrees well with the velocity structure constrained independently by previous studies. Earthquakes in the middle of the strait are dominant in strike-slip and normal slip within 30 km depth. Shallow thrusting events are found only in the Miaoli offshore area of Taiwan. As for the 2018 Taiwan Shoal earthquake sequence, it is located right on the region absence of known fault-plane solutions, therefore offers important new constraints. All events of the sequence show high angle strike-slips and shallow centroid depth of 11-21 km, more consistent with seismicity determined by Fujian seismic center. This event is far away from the M8 1604 Quanzhou earthquake, and is also clearly unrelated to the structure of 1994 M<sub>w </sub>6.7 normal-faulting event in Tainan Basin. The 2018 sequence is probably the reactivation of a pre-existing normal fault that was created by rifting during the Cenozoic.</p><p>  For future work, we will re-evaluate the MTs of M>5.5 intermediate-depth earthquakes of the Ryukyu subduction zone by including waveforms of stations YNG and IGK from Japan network in the inversion. We will also test different upper mantle velocities in the model for the computation of Green’s functions. We anticipate that our work can provide a set of parameters more suitable for the MT inversion, and the MT results can delineate the Ryukyu subduction zone properties better.</p><p> </p><p>keywords : Taiwan Strait, focal mechanisms, moment tensor inversion</p>

The Productivity of Cascadia Aftershock Sequences

2021 ◽  
Author(s):  
Joan Gomberg ◽  
Paul Bodin
Keyword(s):  
Pacific Northwest ◽  
Subduction Zones ◽  
Geological Survey ◽  
Clear Correlation ◽  
Seismogenic Fault ◽  
Intermediate Depth ◽  
Aftershock Sequences ◽  
Intraslab Earthquake ◽  
Seismicity Rates ◽  
Background Seismicity

ABSTRACT This study addresses questions about the productivity of Cascadia mainshock–aftershock sequences using earthquake catalogs produced by the Geological Survey of Canada and the Pacific Northwest Seismic Network. Questions concern the likelihood that future moderate to large intermediate depth intraslab earthquakes in Cascadia would have as few detectable aftershocks as those documented since 1949. More broadly, for Cascadia, we consider if aftershock productivities vary spatially, if they are outliers among global subduction zones, and if they are consistent with a physical model in which aftershocks are clock-advanced versions of tectonically driven background seismicity. A practical motivation for this study is to assess the likely accuracy of aftershock forecasts based on productivities derived from global data that are now being issued routinely by the U.S. Geological Survey. For this reason, we estimated productivity following the identical procedures used in those forecasts and described in Page et al. (2016). Results indicate that in Cascadia we can say that the next intermediate depth intraslab earthquake will likely have just a few detectable aftershocks and that aftershock productivity appears to be an outlier among global subduction zones, with rates that on average are lower by more than half, except for mainshocks in the upper plate. Our results are consistent with a clock-advance model; productivities may be related to the proximity of mainshocks to a population of seismogenic fault patches and correlate with background seismicity rates. The latter and a clear correlation between productivities with mainshock depth indicate that both factors may have predictive value for aftershock forecasting.

scholarly journals Slab stress field in the Hellenic subduction zone as inferred from intermediate-depth earthquakes

2011 ◽  
Vol 63 (2) ◽  
pp. 139-144 ◽  
Author(s):  
S. Rontogianni ◽  
K. I. Konstantinou ◽  
N. S. Melis ◽  
C. P. Evangelidis
Keyword(s):  
Stress Field ◽  
Subduction Zone ◽  
Intermediate Depth ◽  
Hellenic Subduction Zone ◽  
Slab Stress

scholarly journals Tracking subducted ridges through intermediate-depth seismicity in the Vanuatu subduction zone

Geology ◽  
2018 ◽  
Vol 46 (9) ◽  
pp. 767-770 ◽  
Author(s):  
Christian Baillard ◽  
Wayne C. Crawford ◽  
Valérie Ballu ◽  
Bernard Pelletier ◽  
Esline Garaebiti
Keyword(s):  
Subduction Zone ◽  
Intermediate Depth
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