Source parameters and focal mechanisms of local earthquakes: Single broadband observatory at ISM Dhanbad

2009 ◽  
Vol 74 (3) ◽  
pp. 413-419 ◽  
Author(s):  
J. R. Kayal ◽  
V. K. Srivastava ◽  
S. N. Bhattacharya ◽  
P. K. Khan ◽  
Rima Chatterjee
Keyword(s):  
Source Parameters ◽  
Focal Mechanisms ◽  
Local Earthquakes

Seismic doublets and a complex seismic sequence controlled by the rotation of the Juan Fernández microplate

2021 ◽  
Author(s):  
Simone Cesca ◽  
Carla Valenzuela Malebrán ◽  
José Ángel López-Comino ◽  
Timothy Davis ◽  
Carlos Tassara ◽  
...  
Keyword(s):  
Source Parameters ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
Joint Analysis ◽  
Seismic Sequence ◽  
Local Data ◽  
Study Region ◽  
Coulomb Stress Changes ◽  
Earthquake Source Parameters ◽  
Stress Changes

<p> A complex seismic sequence took place in 2014 at the Juan Fernández microplate, a small microplate located between Pacific, Nazca and Antarctica plates. Despite the remoteness of the study region and the lack of local data, we were able to resolve earthquake source parameters and to reconstruct the complex seismic sequence, by using modern waveform-based seismological techniques. The sequence started with an exceptional Mw 7.1-6.7 thrust – strike slip earthquake doublet, the first subevent being the largest earthquake ever recorded in the region and one of the few rare thrust earthquakes in a region otherwise characterized by normal faulting and strike slip earthquakes. The joint analysis of seismicity and focal mechanisms suggest the activation of E-W and NE-SW faults or of an internal curved pseudofault, which is formed in response to the microplate rotation, with alternation of thrust and strike-slip earthquakes. Seismicity migrated Northward in its final phase, towards the microplate edge, where a second doublet with uneven focal mechanisms occurred. The sequence rupture kinematics is well explained by Coulomb stress changes imparted by the first subevent. Our analysis show that compressional stresses, which have been mapped at the northern boundary of the microplate, but never accompanied by large thrust earthquakes, can be accommodated by the rare occurrence of large, impulsive, shallow thrust earthquakes, with a considerable tsunamigenic potential.</p>

Earthquake Source Parameters in Southwestern China and Their Rheological Implications

2020 ◽  
Vol 91 (2A) ◽  
pp. 936-947
Author(s):  
Qingdong Wang ◽  
Risheng Chu
Keyword(s):  
Southern California ◽  
Depth Distribution ◽  
Source Parameters ◽  
Focal Mechanisms ◽  
Yunnan Region ◽  
Brittle Ductile Transition ◽  
Earthquake Source Parameters ◽  
China Earthquake ◽  
International Seismological Centre ◽  
Minimum Moment

Abstract Earthquake depth distribution provides key information on rheological behavior of the crust, which usually shows a brittle–ductile transition at a depth of about 10 km. In this study, we use the generalized cut-and-paste method to obtain source parameters of 571 earthquakes in the Sichuan–Yunnan region of China between 2009 and 2017. We were able to successfully determine focal mechanisms, moment magnitudes, and centroid depths of 536 earthquakes with a minimum moment magnitude of 3.2. Our moment magnitudes and centroid depths are systematically smaller than the magnitudes (Ms and mb) and hypocenter depths from the China Earthquake Network Center and International Seismological Centre catalogs for M≥4.0 earthquakes. The earthquake depths in the Sichuan–Yunnan region are mostly in a 5–9 km range, with an average at 7.6 km. About 23% earthquakes have centroid depths <5  km and are concentrated in the southern Sichuan basin. Only very few earthquakes are deeper than 19 km. Compared with the earthquake depth distribution in southern California, the Sichuan–Yunnan region has many shallower earthquakes. The depth distribution suggests that the brittle–ductile transition in the Sichuan–Yunnan region is shallower than the transition beneath southern California, which is probably due to the existence of newborn faults in the Sichuan–Yunnan region.

scholarly journals Double difference relocation of local earthquakes in the Nepal Himalaya

2013 ◽  
Vol 46 ◽  
Author(s):  
S. Rajaure ◽  
S. N. Sapkota ◽  
L. B. Adhikari ◽  
B. Koirala ◽  
M. Bhattarai ◽  
...  
Keyword(s):  
Seismic Activity ◽  
Focal Mechanisms ◽  
Double Difference ◽  
Simple Explanation ◽  
Fault Plane Solutions ◽  
Motion Data ◽  
Local Earthquakes ◽  
Microseismic Activity ◽  
Narrow Belt ◽  
Himalayan Tectonics

Interseismic strain across the Himalaya is associated with intense microseismic activity. In this study we analyze in detail this seismicity to explore in more details how it relates to Himalayan tectonics. We use the Double Difference Relocation Method to relocate local earthquakes recorded by National Seismological Centre in the period between 1995 and 2003. We also determined fault plane solutions for 10 earthquakes based on waveforms modeling and first P-motion data to complement the existing dataset of focal mechanisms. The results depict a narrow belt of intense seismic activity, at depth between 10 and 20km, which can be traced all along the topographic front of the Higher Himalaya in Nepal. This zone coincides with the zone of interseismic strain build up at the down dip end of the locked portion of the Main Himalayan Thrust fault. These earthquakes probably activate minor faults within the Himalayan wedge, in a volume which experiences stress build up in the interseismic period. The intense seismic activity generally cease abruptly as the elevation of topography gets higher than 3500 m. This elevation also coincides with a change of tectonic regime. Earthquakes within the seismicity belt at front of the Higher Himalaya are of thrust type indicating N-S shortening. Where the topographic elevation is higher than 3500 m focal mechanisms indicate E-W extension. The effect of topography on the regional stress field thus provides a simple explanation for the distribution of focal mechanisms and the seismicity cut-off at the 3500m elevation contour line.

scholarly journals Source parameters, focal mechanisms and stress tensor inversion from moderate earthquakes and its relationship with subduction Zone

2019 ◽  
Vol 58 (2) ◽  
Author(s):  
Tonatiuh Domínguez R. ◽  
Héctor E. Rodríguez Lozoya ◽  
Gabriel Reyes D. ◽  
Luis Quintanar Robles ◽  
Armando Aguilar Meléndez ◽  
...  
Keyword(s):  
Stress Tensor ◽  
Subduction Zone ◽  
Source Parameters ◽  
Focal Mechanisms ◽  
Stress Tensor Inversion

Seismic Source Processes of 25 Earthquakes (Mw>5) in the Gulf of California

2022 ◽  
Author(s):  
Eduardo Huesca-Pérez ◽  
Edahí Gutierrez-Reyes ◽  
Luis Quintanar
Keyword(s):  
Gulf Of California ◽  
Moment Tensor ◽  
Source Parameters ◽  
Seismic Source ◽  
Focal Mechanisms ◽  
Process Models ◽  
Moment Tensors ◽  
Time Space ◽  
Double Couple ◽  
Broadband Seismograms

ABSTRACT The Gulf of California (GoC) is a complex tectonic boundary that has been instrumented in the past several decades to record broadband seismograms. This volume of data has allowed us to study several source parameters systematically. Before, only a few source parameters of earthquakes greater than magnitude five had been studied in the GoC area. We re-examined the focal mechanisms of several earthquakes in the southern GoC that occurred over the last 20 yr using local–regional distance broadband seismograms. These focal mechanisms were then used as input data to retrieve the time–space history of the rupture for each earthquake. This work contributes to the study of 25 rupture-process models computed with the method proposed by Yagi et al. (1999). To investigate more about the nature of the seismicity in the GoC, we also calculated the non-double-couple component of moment tensors for 45 earthquakes. Previous studies (e.g., Ortega et al., 2013, 2016) have shown that non-double-couple components from moment tensors in this region are associated with complex faulting, suggesting that oblique faults or several parallel faults are interacting simultaneously. Our results show that, at least for moderate earthquakes (5 < M < 6), rupture processes in the GoC show a complex interaction between fault systems. It is revealed on the important contribution of non-double-couple component obtained in the full moment tensor analysis.

A seismological study of two Attica, New York earthquakes

1978 ◽  
Vol 68 (3) ◽  
pp. 641-651 ◽  
Author(s):  
Robert B. Herrmann
Keyword(s):  
New York ◽  
Source Parameters ◽  
Focal Depth ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
The Other ◽  
Nodal Plane ◽  
Reverse Faulting ◽  
Epicentral Intensity ◽  
East West

abstract The Attica, New York earthquakes of January 1, 1966 and June 12, 1967 are studied in detail to obtain their focal mechanisms, depths and seismic moments. Both events have similar source parameters with one nodal plane striking about 120° and dipping 60°S and the other nodal plane striking about 20° and dipping 70°E. The fault motion on the NNE nodal plane has a component of right lateral strike slip and one of reverse faulting. Though this nodal plane parallels the Clarendon-Linden structure, the possibility of associating the other nodal plane with a diffuse east-west seismicity trend cannot be excluded. The shallow focal depth of 2 to 3 km for these two events can be used as an explanation of the relatively high epicentral intensity VIII of the Attica event of 1929.

Sign in / Sign up

Export Citation Format

Share Document