Shallow slip of blind fault associated with the 2019 Ms 6.0 Changning earthquake in fold-and-thrust belt in salt mines of Southeast Sichuan, China

2020 ◽  
Vol 224 (2) ◽  
pp. 909-922
Author(s):  
Ying-Hui Yang ◽  
Jyr-Ching Hu ◽  
Qiang Chen ◽  
Xinglin Lei ◽  
Jingjing Zhao ◽  
...  
Keyword(s):  
Shale Gas ◽  
Main Shock ◽  
Failure Stress ◽  
Stress Change ◽  
Thrust Belt ◽  
Coulomb Failure Stress ◽  
Fold And Thrust Belt ◽  
Coulomb Failure Stress Change ◽  
Coulomb Failure ◽  
Salt Mining

SUMMARY An earthquake with a magnitude of Ms 6.0 and shallow focal depth of ∼4 km struck the Changning county, Sichuan province, China on 2019 June 17. The hypocentre is located in the fold-and-thrust belt with plentiful shale gas and salt mine resources. One hypothesis is that the shallow fault could be affected by the artificial pressure water injection including the disposal of wastewater, fracking shale gas extraction and salt mining in Changning area. In this study, SAR (Synthetic Aperture Radar) images, historical earthquakes, aftershocks and seismic reflection data were collected to jointly investigate the characteristics of the 2019 Changning earthquake. The source model inferred from the InSAR coseismic deformation observation reveals that the 2019 Changning earthquake is attributed to a blind fault dipping to southwest with dominant thrust and sinistral strike slip. Moreover, a small shallow fault developing within the Changning anticline was triggered by the main shock, which contributed to the surface displacements as observed in the north of the epicentre. The estimated maximum slip of 0.49 m is located at the depth of ∼1.9 km, ∼9 km northwest of the epicentre. The Coulomb failure stress change caused by the previous two large earthquakes, which occurred in the hydraulic fracturing area, suggesting that they have little effect on the initial rupture of the 2019 Changning earthquake. Despite this, they have a positive triggering effect on the fault rupture in the northwest of the seismogenic fault. In addition, the analysis on the relation between the positive Coulomb failure stress change and the aftershocks suggests that the aftershocks may have different motion patterns from the main shock. The analysis also shows the earthquakes occurrence in the seismogenic zone may be affected by the high pore pressure due to the long-term injection of salt mining for more than three decades.

Induced or triggered? The deadly February 2019 Rongxian-Weiyuan ML 4.9 earthquake in the shale gas field in Sichuan, China

2020 ◽  
Author(s):  
Hongfeng Yang ◽  
Pengcheng Zhou ◽  
Nan Fang ◽  
Gaohua Zhu ◽  
Wenbin Xu ◽  
...  
Keyword(s):  
Shale Gas ◽  
Fault Injection ◽  
Stress Transfer ◽  
Gas Production ◽  
Failure Stress ◽  
Injection Wells ◽  
Gas Field ◽  
Coulomb Failure Stress ◽  
Coulomb Failure Stress Change ◽  
Coulomb Failure

<p>Coinciding with the extensive hydraulic fracturing activities in the southern Sichuan basin, seismicity in the region has surged in the past a few years, including a number of earthquakes with magnitudes larger than 5. On 25 February 2019, an M<sub>L</sub>4.9 earthquake struck the Rongxian County, Sichuan, China and caused 2 fatalities and 12 injuries, the first deadly earthquake associated with shale gas production. The earthquake was preceded by two foreshocks with magnitudes of M<sub>L</sub>4.7 and M<sub>L</sub>4.3 within two days. We relocated the earthquake sequence using local and regional seismic network, and obtained the focal depths of the mainshock and two foreshocks at 1 and 3 km, respectively, much shallower than the report from catalogue. Most other smaller quakes were located at 2-6 km. The mainshock had also been well captured by InSAR images, which confirmed the shallow depth of ~1 km. Both seismic and geodetic data yielded thrust faulting mechanism for the mainshock, consistent with the mapped Molin fault in the region. The two foreshocks, however, occurred on an unmapped fault that has different orientation than the Molin fault. Injection wells are found in the vicinity of the two foreshocks and the fracking depth (~2.7 km) coincides with their focal depths, suggesting a possible causal relationship. The mainshock is located in the region with positive Coulomb failure stress caused the two foreshocks. The value of Coulomb failure stress change is 0.03 bar, smaller than the typical static triggering threshold. Therefore, the mainshock is likely caused by fracking by poroelastic stress transfer.</p>

scholarly journals The 2014 Mw 6.1 Ludian Earthquake: The Application of RADARSAT-2 SAR Interferometry and GPS for this Conjugated Ruptured Event

2019 ◽  
Vol 12 (1) ◽  
pp. 99
Author(s):  
Yufen Niu ◽  
Shuai Wang ◽  
Wu Zhu ◽  
Qin Zhang ◽  
Zhong Lu ◽  
...  
Keyword(s):  
Main Shock ◽  
Surface Deformation ◽  
Large Earthquake ◽  
Failure Stress ◽  
Sar Interferometry ◽  
Coseismic Deformation ◽  
Coulomb Failure Stress ◽  
Ludian Earthquake ◽  
Stress Changes ◽  
Coulomb Failure

Although the Zhaotong–Ludian fault is a seismically active zone located in the boundary between the Sichuan–Yunnan block and the South China block, it has not experienced a large earthquake greater than Mw 7 since at least 1700. On 3 August, 2014, an Mw 6.1 earthquake (the Ludian earthquake) ruptured the Zhaotong active belt in Ludian County, Yunnan province, China. This earthquake was the largest earthquake recorded in the region since 2000, and it provides us with a unique opportunity to study the active tectonics in the region. The analysis of the aftershocks showed that two conjugate faults could have been involved in the event. We first used Global Positioning System (GPS) data and C-band RADARSAT-2 imagery to map the coseismic surface deformation. We then inverted the derived coseismic deformation for the slip distribution based on the constructed conjugate fault model. Finally, the coulomb failure stress due to the Ludian earthquake was estimated to investigate the potential seismic hazards in this region. Our investigations showed that the Ludian earthquake was mainly a bilateral rupture event. The major slip of the main shock was located at depths of 0–5 km, which is close but does not superpose with the aftershocks that are mostly located at depths of 5–20 km. Interestingly, the seismic moment released by the aftershocks (6.9 × 1018 N∙m) was greater than that of the main shock (2.6 × 1018 N∙m). This evidence suggests that the accumulated elastic strain at depths of 0–20 km could have been fully released by the Ludian earthquake and its subsequent aftershocks. Furthermore, our analysis of the coulomb failure stress changes due to the main shock showed that the aftershocks could be the result of dynamic triggering rather than static triggering.

Complete Coulomb Failure Stress Changes and Stress Triggering of Yunnan Longling Earthquake Sequence

2007 ◽  
Vol 50 (4) ◽  
pp. 963-974 ◽  
Author(s):  
Xiao-Ping WU ◽  
Hong FU ◽  
Bouchon MICHAEL ◽  
Jia-Fu HU ◽  
Yi-Li HU ◽  
...  
Keyword(s):  
Failure Stress ◽  
Earthquake Sequence ◽  
Coulomb Failure Stress ◽  
Stress Changes ◽  
Coulomb Failure ◽  
Stress Triggering ◽  
Coulomb Failure Stress Changes

scholarly journals Fault Instability and Its Relation to Static Coulomb Failure Stress Change in the 2016 Mw 6.5 Pidie Jaya Earthquake, Aceh, Indonesia

2021 ◽  
Vol 8 ◽  
Author(s):  
Dian Kusumawati ◽  
David P. Sahara ◽  
Sri Widiyantoro ◽  
Andri Dian Nugraha ◽  
Muzli Muzli ◽  
...  
Keyword(s):  
Fault Plane ◽  
Fault Analysis ◽  
Stress Change ◽  
Instability Criterion ◽  
Coulomb Stress Change ◽  
Instability Analysis ◽  
Aftershock Distribution ◽  
Coulomb Failure Stress Change ◽  
Coulomb Failure ◽  
Sumatran Fault

Herein, we applied the fault instability criterion and integrated it with the static Coulomb stress change (ΔCFS) to infer the mechanism of the 2016 Mw 6.5 Pidie Jaya earthquake and its aftershock distribution. Several possible causative faults have been proposed; however, the existence of a nearby occurrence, the 1967 mb 6.1 event, created obscurity. Hence, we applied the fault instability analysis to the Pidie Jaya earthquake 1) to corroborate the Pidie Jaya causative fault analysis and 2) to analyze the correlation between ΔCFS distribution imparted by the mainshock and the fault instability of the reactivated fault planes derived from the focal solution of the Pidie Jaya aftershocks. We performed the fault instability analysis for two possible source faults: the Samalanga-Sipopok Fault and the newly inferred Panteraja Fault. Although the maximum instability value of the Samalanga-Sipopok Fault is higher, the dip value of the Panteraja Fault coincides with its optimum instability. Therefore, we concluded that Panteraja was the causative fault plane. Furthermore, a link between the 1967 mb 6.1 event and the 2016 Mw 6.5 earthquake is discussed. To analyze the correlation between the fault instability and the ΔCFS, we resolved the ΔCFS of the Pidie Jaya mainshock on its aftershock planes and compared the ΔCFS results with the fault instability calculation on each aftershock plane. We discussed the possibility of conjugate failure as shown by the aftershock fault instability. Related to the ΔCFS and fault instability comparison, we found that not all the aftershocks have positive ΔCFSs, but their instability value is high. Thus, we suggest that the fault plane instability plays a role in events that do not occur in positive ΔCFS areas. Apart from these, we also showed that the off-Great Sumatran Fault (Panteraja and Samalanga-Sipopok Faults) are unstable in the Sumatra regional stress setting, thereby making it more susceptible to slip movement.

scholarly journals Is Coulomb Stress the Best Choice for Aftershock Forecasting?

2021 ◽  
Author(s):  
Shubham Sharma ◽  
Sebastian Hainzl ◽  
Gert Zöller ◽  
Matthias Holschneider
Keyword(s):  
Probabilistic Model ◽  
Size Variation ◽  
Roc Curves ◽  
Failure Stress ◽  
Coulomb Stress ◽  
Coulomb Failure Stress ◽  
Coulomb Failure ◽  
Large Earthquakes ◽  
Simple Stress ◽  
Better Than

<p>The Coulomb failure stress (CFS) criterion is the most commonly used method for predicting spatial distributions of aftershocks following large earthquakes. However, large uncertainties are always associated with the calculation of Coulomb stress change. The uncertainties mainly arise due to nonunique slip inversions and unknown receiver faults; especially for the latter, results are highly dependent on the choice of the assumed receiver mechanism. Based on binary tests (aftershocks yes/no), recent studies suggest that alternative stress quantities, a distance‐slip probabilistic model as well as deep neural network (DNN) approaches, all are superior to CFS with predefined receiver mechanism. To challenge this conclusion, which might have large implications, we use 289 slip inversions from SRCMOD database to calculate more realistic CFS values for a layered half‐space and variable receiver mechanisms. We also analyze the effect of the magnitude cutoff, grid size variation, and aftershock duration to verify the use of receiver operating characteristic (ROC) analysis for the ranking of stress metrics. The observations suggest that introducing a layered half‐space does not improve the stress maps and ROC curves. However, results significantly improve for larger aftershocks and shorter time periods but without changing the ranking. We also go beyond binary testing and apply alternative statistics to test the ability to estimate aftershock numbers, which confirm that simple stress metrics perform better than the classic Coulomb failure stress calculations and are also better than the distance‐slip probabilistic model.</p>

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