In-situ observation of pre-, co- and post-seismic shear slip at 1.5 km depth

Journal Article · Wed Apr 07 04:00:00 EDT 2021

DOI:https://doi.org/10.1002/essoar.10506700.1· OSTI ID:1826709

Schoenball, Martin ^[1]; Guglielmi, Yves ^[1]; Ajo-Franklin, Jonathan Blair ^[2]; Cook, Paul J. ^[1]; Dobson, Patrick ^[1]; Hopp, Chet ^[1]; Kneafsey, Timothy J. ^[1]; Soom, Florian ^[1]; Ulrich, Craig ^[1]

---

1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2. Rice Univ., Houston, TX (United States)

Understanding the initiation and arrest of earthquakes is one of the long-standing challenges of seismology. Here we report on direct observations of borehole displacement by a meter-sized shear rupture induced by pressurization of metamorphic rock at 1.5 km depth. We observed the acceleration of sliding, followed by fast co-seismic slip and transient afterslip. Total displacements were about 7, 5.5 and 9.5 micrometers, respectively for the observed pre-slip, co-seismic slip and afterslip. The observed pre-slip lasted about 0.4 seconds. Co-seismic slip was recorded by the 1 kHz displacement recording and a 12-component array of 3-C accelerometers sampled at 100 kHz. The observed afterslip is consistent with analytical models of arrest in a velocity-strengthening region and subsequent stress relaxation. < p >The observed slip vector agrees with the activation of a bedding plane within the phyllite, which is corroborated by relocated seismic events that were observed during the later stages of the injection experiment.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 1826709
• Country of Publication: United States
• Language: English