Strong Aftershock Study Based on Coulomb Stress Triggering—A Case Study on the 2016 Ecuador Mw 7.8 Earthquake

Abstract

Abstract:The 2016 Ecuador M 7.8 earthquake ruptured the subduction zone boundary between the Nazca plate and the South America plate. This M 7.8 earthquake may have promoted failure in the surrounding crust, where six M ≥ 6 aftershocks occurred following this mainshock. These crustal ruptures were triggered by the high coulomb stress changes produced by the M 7.8 mainshock. Here, we investigate whether the six M ≥ 6 aftershocks are consistent with the positive coulomb stress region due to the mainshock. To explore the correlation between the mainshock and the aftershocks, we adopt a recently published high-quality finite fault model and focal mechanisms to study the coulomb stress triggers during the M 7.8 earthquake sequence. We compute the coulomb failure stress changes (∆CFS) on both of the focal mechanism nodal planes. We compare the ∆CFS imparted by the M 7.8 mainshock on the subsequent aftershocks with the epicenter location of each aftershock. In addition, the shear stress, normal stress, and coulomb stress changes in the focal sources of each aftershock are also computed. Coulomb stress changes in the focal source for the six M ≥ 6 aftershocks are in the range of −2.17-7.564 bar. Only one computational result for the M 6.9 aftershock is negative; other results are positive. We found that the vast majority of the six M ≥ 6 aftershocks occurred in positive coulomb stress areas triggered by the M 7.8 mainshock. Our results suggest that the coulomb stress changes contributed to the development of the Ecuador M 7.8 earthquake sequence.

Coulomb Stress Analysis of Halmahera Earthquake on June 7th 2016, Mw=6.3 and Its Correlation with Aftershocks

“…The previous study showed that the µ' is typically found to be around 0.4 for subduction zones [10]. Figure 6 shows Coulomb stress change distribution of Halmahera earthquake on June 7th, 2016 with depth of 47 km and Mw: 6.3.…”

Unravelling seismogenesis and characterizing the unique features of two significant felt earthquakes (M > 4.0) of 2020 in the southwestern parts of the Delhi region

“…In addition, various researchers have assimilated the fault plane solutions in computing the Coulomb stress variation (Hardebeck et al, 1998;Meier et al, 2014;Asayesh et al, 2020). Furthermore, using the Coulomb stress analysis, several researchers have inferred that the fault planes may undergo induced stress along the nodal planes ( Wu et al, 2017;Asayesh et al, 2020). The present study is focused on two consequent significant earthquakes (M4.6 of July 2020 and M4.2 of December 2020) that had occurred in the northern part of the Alwar district and to the southwest of the Delhi NCR, within a very short span of time of about 5 months.…”

Shelter site location under multi-hazard scenarios

“…According to Utsu (1970) , for a main earthquake with a magnitude of 7, the time difference is generally in the range 0.01-100 days and the range gets larger with the magnitude of main shock. To give examples, for 1999 Marmara Earthquake, the largest aftershock is 27 days later than the main shock ( Örgülü and Aktar, 2001 ), and this time is 17 and 32 days for 2015 Nepal ( Wikipedia, 2018 ) and 2016 Ecuador ( Wu et al, 2017 ) earthquakes, respectively.…”