Aftershock sequences of intermediate-depth earthquakes in the Pamir-Hindu Kush Seismic Zone

The Pamir and Hindu Kush are examples of a puzzling collision system where a complex junction of colliding lithospheric plates coexists with intermediate depth seismicity at 300 km. In this study, we constructed a new tomography model using travel time data from local events recorded by the TIPAGE (Tien Shan – Pamir Geodynamic program) network. In addition to the P- and S-wave velocities down to 200 km, we derived the azimuthal anisotropy. The velocity anomalies were consistent with the results of previous studies. In the crust, the velocity structure and anisotropy directions were mainly oriented along major suture zones. At depths of 80–120 km, a narrow low-velocity anomaly coinciding with the distribution of deep seismicity was interpreted as a trace of entrained crustal material by the dipping lithosphere. The anisotropy directions at these depths were mainly oriented northwest–southeast and were interpreted as indicating the direction of the motion of colliding plates. The difference in the magnitude of anisotropy south and north of the Pamir seismic zone suggests that the lithosphere coming from the south possesses less anisotropy than that of the Asian plate. The local tomography model was supplemented by previously computed regional tomography that expanded the area both laterally and axially. Beneath the Pamir, both continental plates coming from the north and south form a drop-shaped anomaly that will possibly delaminate in time. Beneath the Hindu Kush, we could clearly trace a continuous almost vertical subduction of the Katawaz block from the south. Thus, the continental collision beneath the Pamir and subduction beneath the Hindu Kush are separate processes with different rates and directions of plate movement.

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Spatiotemporal characteristics of aftershock sequences in the South Iceland Seismic Zone: interpretation in terms of pore pressure diffusion and poroelasticity

Geophysical Journal International ◽

10.1111/j.1365-246x.2010.04812.x ◽

2010 ◽

Vol 183 (3) ◽

pp. 1104-1118 ◽

Cited By ~ 6

Author(s):

Mattias Lindman ◽

Björn Lund ◽

Roland Roberts

Keyword(s):

Pore Pressure ◽

Seismic Zone ◽

The South ◽

Spatiotemporal Characteristics ◽

Pressure Diffusion ◽

Aftershock Sequences ◽

South Iceland Seismic Zone

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Geodynamic processes of the continental deep subduction: constraints from the fine crustal structure beneath the Pamir Plateau

10.5194/egusphere-egu2020-12873 ◽

2020 ◽

Author(s):

Wei Li ◽

Yun Chen ◽

Ping Tan ◽

Xiaohui Yuan

Keyword(s):

Spatial Configuration ◽

Spline Interpolation ◽

Joint Inversion ◽

Receiver Functions ◽

Crustal Material ◽

Seismic Zone ◽

S Wave ◽

Low Velocity ◽

Crust And Upper Mantle ◽

Intermediate Depth

<p>The Pamir plateau, located north of the western syntaxis of the India&#173;&#8211;Eurasia collision system, is regarded as one of the most possible places of the ongoing continental deep subduction. Based on a N-S trending linear seismic array across the Pamir plateau, we use the methods of harmonic analysis of receiver functions and the cubic spline interpolation of surface wave dispersions to coordinate their resolutions, and perform a joint inversion of these datasets to construct a 2-D S-wave velocity model of the crust and uppermost mantle. A spatial configuration among the intermediate-depth seismicity, Moho topography, and low-velocity zone(LVZ)s within the crust and upper mantle is revealed. The intermediate-depth seismic zone is enclosed in a mantle LVZ which extends upward to the crustal root and connects with a lower crustal LVZ in the northern Pamir. Just above it, another crustal LVZ is collocated with a Moho uplift. These results not only further confirm the deep subduction of the Asian lower continental crust beneath the Pamir plateau, but also indicate the importance of the metamorphic dehydration of the subducting continental crustal material in the genesis of the intermediate-depth seismicity and crustal deformation.</p>

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The Pamir-Hindu Kush seismic zone as a strain marker for flow in the upper mantle

Tectonics ◽

10.1029/1999tc900062 ◽

2000 ◽

Vol 19 (1) ◽

pp. 103-115 ◽

Cited By ~ 42

Author(s):

Gary L. Pavlis ◽

Shamita Das

Keyword(s):

Upper Mantle ◽

Seismic Zone ◽

Hindu Kush

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Abundant aftershock sequence of the 2015 Mw7.5 Hindu Kush intermediate-depth earthquake

Geophysical Journal International ◽

10.1093/gji/ggy016 ◽

2018 ◽

Vol 213 (2) ◽

pp. 1121-1134 ◽

Cited By ~ 4

Author(s):

Chenyu Li ◽

Zhigang Peng ◽

Dongdong Yao ◽

Hao Guo ◽

Zhongwen Zhan ◽

...

Keyword(s):

Aftershock Sequence ◽

Intermediate Depth ◽

Hindu Kush ◽

Intermediate Depth Earthquake

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Present-day stress field pattern in the Vrancea seismic zone (Romania) deduced from earthquake focal mechanism inversion

Annals of Geophysics ◽

10.4401/ag-8632 ◽

2021 ◽

Vol 64 (6) ◽

pp. PE660

Author(s):

Andrei Bala ◽

Mircea Radulian ◽

Dragos Toma-Danila

Keyword(s):

Large Strain ◽

Average Energy ◽

Seismogenic Zone ◽

Field Pattern ◽

Seismic Zone ◽

Depth Level ◽

Stress Regime ◽

Intermediate Depth ◽

Eastern Carpathians ◽

Earthquake Focal Mechanism

Vrancea seismogenic zone in the South-Eastern Carpathians is characterized by localized intermediate-depth seismicity. Due to its complex geodynamics and large strain release, Vrancea represents a key element in the Carpatho-Pannonian system. Data from a recently compiled catalogue of fault plane solutions (REFMC) are inverted to evaluate stress regime in Vrancea on depth. A single predominant downdip extensive regime is obtained in all considered clusters, including the crustal layers located above the Vrancea slab. The prevalent stress regime confirms previous investigations and requires some mantle-crust coupling. The S3 principal stress is close to vertical, while S1 and S2 are horizontal, oriented perpendicularly and respectively tangentially to the Carpathians Arc bend. This configuration is present at any depth level. According to seismicity patterns, there are two main active segments in the Vrancea intermediate-depth domain, at 55 – 105 km and 105 – 180 km, both able to generate major events. The configuration of the tectonic stresses as resulted from inversion is similar in both segments. Also, high fault instability (I > 0.95) is characterizing the segments. The only notable difference is given by the friction and stress ratio parameters which drop down in the bottom segment from μ = 0.95 to μ = 0.55 and from R = 0.51 to R = 0.29. This variation is attributed to possible weakening processes activated below 100 km depth and can explain the intensification of seismicity production as earthquake rate and average energy release in the lower segment versus the upper segment.

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