Seminar: Modelling induced earthquake sequences Event as iCalendar

01 April 2015

2 - 3pm

Venue: Room 439.G10

Location: Ground Level, UniServices House, 70 Symonds Street

Host: Dr Richard Clarke

Contact email: rj.clarke@auckland.ac.nz

 

A Department of Engineering Science research seminar by David Dempsey of Stanford University, USA.

 

Abstract:

Seismicity in the central and eastern United States has increased by several orders of magnitude in the past decade. This increase is largely attributed to the injection of high-volumes of saltwater - mainly in Oklahoma - into deep formations overlying Precambrian crystalline basement. The resulting fluid overpressure reduces the shear strength of critically stressed, permeable basement faults, and ultimately leads to triggered earthquakes.

Observations of induced earthquake sequences reveal many interesting behaviors, including spatiotemporal migration of the events, variations in seismicity rate with injection, departure from traditional frequency-magnitude (Gutenberg-Richter) relationships, and time delays between injection and earthquake activity. Modeling these behaviors requires a simulation tool that captures fluid injection, pressure evolution and geomechanical stress changes in the reservoir as well as the earthquake rupture process, ie, nucleation, propagation, arrest and associated fault slip and stress drop distribution. We have developed such a simulator by coupling a quasidynamic spectral boundary integral method to an existing reservoir simulator (FEHM and PFLOTRAN).

In this talk, I will describe the earthquake rupture physics that the new simulator captures, demonstrate several benchmark problems, and conclude with a more realistic simulation of seismicity induced on basement faults that has intriguing implications for rupture directivity.