The Stress Field in the Northern Apulia (Southern Italy), as Deduced from Microearthquake Focal Mechanisms: New Insight from Local Seismic Monitoring

2020 ◽  
pp. 914-927
Author(s):  
Marilena Filippucci ◽  
Pierpaolo Pierri ◽  
Salvatore de Lorenzo ◽  
Andrea Tallarico
Keyword(s):  
Stress Field ◽  
Southern Italy ◽  
Seismic Monitoring ◽  
Focal Mechanisms

scholarly journals Seismogenic Structure Orientation and Stress Field of the Gargano Promontory (Southern Italy) From Microseismicity Analysis

2021 ◽  
Vol 9 ◽  
Author(s):  
Simona Miccolis ◽  
Marilena Filippucci ◽  
Salvatore de Lorenzo ◽  
Alberto Frepoli ◽  
Pierpaolo Pierri ◽  
...  
Keyword(s):  
Stress Field ◽  
Southern Italy ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
Seismic Network ◽  
Maximum Magnitude ◽  
Fault Plane Solutions ◽  
Seismicity Pattern ◽  
The Past ◽  
Gargano Promontory

Historical seismic catalogs report that the Gargano Promontory (southern Italy) was affected in the past by earthquakes with medium to high estimated magnitude. From the instrumental seismicity, it can be identified that the most energetic Apulian sequence occurred in 1995 with a main shock of MW = 5.2 followed by about 200 aftershocks with a maximum magnitude of 3.7. The most energetic earthquakes of the past are attributed to right-lateral strike-slip faults, while there is evidence that the present-day seismicity occur on thrust or thrust-strike faults. In this article, we show a detailed study on focal mechanisms and stress field obtained by micro-seismicity recorded from April 2013 until the present time in the Gargano Promontory and surrounding regions. Seismic waveforms are collected from the OTRIONS Seismic Network (OSN), from the Italian National Seismic Network (RSN), and integrated with data from the Italian National Accelerometric Network (RAN) in order to provide a robust dataset of earthquake localizations and focal mechanisms. The effect of uncertainties of the velocity model on fault plane solutions (FPS) has been also evaluated indicating the robustness of the results. The computed stress field indicates a deep compressive faulting with maximum horizontal compressive stress, SHmax, trending NW-SE. The seismicity pattern analysis indicates that the whole crust is seismically involved up to a depth of 40 km and indicates the presence of a low-angle seismogenic surface trending SW-NE and dipping SE-NW, similar to the Gargano–Dubrovnik lineament. Shallower events, along the eastern sector of the Mattinata Fault (MF), are W-E dextral strike-slip fault. Therefore, we hypothesized that the seismicity is locally facilitated by preexisting multidirectional fractures, confirmed by the heterogeneity of focal mechanisms, and explained by the different reactivation processes in opposite directions over the time, involving the Mattinata shear zone.

scholarly journals Focal mechanisms and stress field in the Atotsugawa fault area, central Honshu, Japan

2010 ◽  
Vol 62 (4) ◽  
pp. 367-380 ◽  
Author(s):  
Kei Katsumata ◽  
◽  
Masahiro Kosuga ◽  
Hiroshi Katao
Keyword(s):  
Stress Field ◽  
Focal Mechanisms ◽  
Atotsugawa Fault

scholarly journals The Crustal Stress Field Inferred from Focal Mechanisms in Northern Chile

2021 ◽  
Author(s):  
Carlos Herrera ◽  
John F. Cassidy ◽  
Stan E. Dosso ◽  
Jan Dettmer ◽  
Wasja Bloch ◽  
...  
Keyword(s):  
Stress Field ◽  
Focal Mechanisms ◽  
Northern Chile ◽  
Crustal Stress ◽  
Crustal Stress Field

Spatial variation in the present-day stress field and tectonic regime of Northeast Tibet from moment tensor solutions of local earthquake data

2020 ◽  
Vol 221 (1) ◽  
pp. 478-491 ◽  
Author(s):  
Zhengyang Pan ◽  
Jiankun He ◽  
Zhigang Shao
Keyword(s):  
Stress Field ◽  
Compressive Stress ◽  
Moment Tensor ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
Qilian Mountains ◽  
Compression Axis ◽  
The South ◽  
Maximum Compression ◽  
Stress Orientation

SUMMARY Focal mechanism solutions and their predicted stress pattern can be used to investigate tectonic deformation in seismically active zones and contribute to understanding and constraining the kinematic patterns of the outward growth and uplift of the Tibetan Plateau. Herein, we determined the focal mechanisms of 398 earthquakes in Northeast Tibet recorded by the China National Seismic Network (CNSN) by using the cut-and-paste method. The results show that the earthquakes predominately exhibited thrust and strike-slip faulting mechanisms with very few normal events. We then combined the derived focal mechanisms with global centroid moment tensor (GCMT) catalogue solutions and previously published solutions to predict the regional distribution of the stress field through a damped linear inversion. The inversion results show that most of region is dominated by a thrust faulting regime. From the southern East Kunlun fault in the west to the northern Qilian Mountains along the Altyn Tagh fault (ATF), the maximum compression axis rotates slightly clockwise; farther to the south of the Haiyuan fault in the east, there is an evident clockwise rotation of the maximum compression axis, especially at the eastern end of the Haiyuan fault. In the Qilian Mountains, the axis of the compressive stress orientation approximately trends NE–SW, which does not markedly differ from the direction of India–Eurasia convergence, emphasizing the importance of the compressive stress in reflecting the remote effects of this continental collision. The overall spatial pattern of the principal stress axes is closely consistent with the GPS-derived horizontal surface velocity. A comparison of the stress and strain rate fields demonstrated that the orientations of the crustal stress axes and the surface strain axes were almost identical, which indicates that a diffuse model is more suitable for describing the tectonic characteristics of Northeast Tibet. Additionally, the compressive stress orientation rotated to ENE–WSW in the northern Qilian Mountains along the ATF and to ENE–WSW or E–W along the eastern part of the Haiyuan fault and its adjacent area to the south, highlighting the occurrence of strain partitioning along large left-lateral strike-slip faults or the lateral variation of crustal strength across these faults. Combining geodetic, geological and seismological results, we suggest that a hybrid model incorporating both the diffuse model associated with shortening and thickening of the upper crust and the asthenospheric flow model accounting for the low-velocity zone in the middle-lower crust may reflect the primary mode of crustal deformation in Northeast Tibet.

Stress field in the Transcarpathians from focal mechanisms

2017 ◽  
Author(s):  
D.V. Malytskyy ◽  
A.V. Murovska ◽  
O.O. Obidina ◽  
O.B. Gintov ◽  
A.R. Gnyp ◽  
...  
Keyword(s):  
Stress Field ◽  
Focal Mechanisms
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