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Earthquake Triggering in the Context of 2019 Ridgecrest Earthquake Sequence

Description: 

2019 Mw 7.1 Ridgecrest earthquake sequence provides an interesting case to study different modes of earthquake triggering. The mainshock is preceded by a Mw 6.4 foreshock that occurred 34 hours earlier. It is unclear what role it plays, if any, in triggering the mainshock. Why did it not trigger the mainshock immediately? If it is a case of delayed triggering, what causes the delay? The mainshock is followed by prolific aftershock activity. The aftershock activity is, however, far from uniform in space and time. It still remains enigmatic how afterslip may have triggered aftershocks and contributed to this heterogeneous distribution. Intriguingly, Coso geothermal area, situated just northwest of the main ruptured fault, appears to be indifferent from stress triggering with little change in seismic activity. On the other hand, Garlock fault, immediately south of the mainshock, appears to be triggered by the mainshock with increased seismic activity and slow slip occurring in a segment close to the mainshock (Ross et al., 2019). In addition, we are investigating the pre-seismic time period (before 2019) spanning several decades. We have built an earthquake catalog based on machine learning (Zhou et al., 2019) that has captured a more complete picture of seismic activity leading to the 2019 Ridgecrest earthquake sequence. We show that a large part of the fault that ruptured in 2019 can be discernable via microseismic activity. It may also indicate stress build-up along this fault before the sequence starts. Interestingly, we found several doublet repeaters in this are including some on or very close to the fault that ruptured in 2019. It is interesting to note that repeaters are reported during the 2019 Ridgecrest sequence (Huang et al., 2020). Overall, this area shows evidence of a variety of triggering phenomena – from potentially delayed triggering to triggered slow slip – making it an interesting case to study. Our new long-term earthquake catalog based on machine learning is providing new insights into the processes of triggering and underlying physics.

Session: New Observations and Modeling of Triggered Seismicity

Type: Oral

Date: 4/19/2023

Presentation Time: 04:45 PM (local time)

Presenting Author: Abhijit Ghosh

Student Presenter: No

Invited Presentation: 

Authors