Essential Site Maintenance: Authorea-powered sites will be updated circa 15:00-17:00 Eastern on Tuesday 5 November.
There should be no interruption to normal services, but please contact us at [email protected] in case you face any issues.

loading page

In-situ observation of pre-, co- and post-seismic shear slip at 1.5 km depth
  • +6
  • Martin Schoenball,
  • Yves Guglielmi,
  • Jonathan Blair Ajo-Franklin,
  • Paul J Cook,
  • Patrick Dobson,
  • Chet Hopp,
  • Timothy J Kneafsey,
  • Florian Soom,
  • Craig Ulrich
Martin Schoenball
Lawrence Berkeley National Laboratory

Corresponding Author:[email protected]

Author Profile
Yves Guglielmi
Lawrence Berkeley National Laboratory
Author Profile
Jonathan Blair Ajo-Franklin
Rice University
Author Profile
Paul J Cook
LBNL
Author Profile
Patrick Dobson
Lawrence Berkeley National Laboratory (DOE)
Author Profile
Chet Hopp
Lawrence Berkeley National Laboratory
Author Profile
Timothy J Kneafsey
Lawrence Berkeley Laboratory
Author Profile
Florian Soom
Lawrence Berkeley National Laboratory
Author Profile
Craig Ulrich
Lawerence Berkeley National Laboratory
Author Profile

Abstract

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. 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.