Tremor Map and Catalog
With a grant from the Moore Foundation, the BSL is installing TremorScope, four borehole and four surface stations positioned to record deep tremor along the San Andreas Fault in central California. Above: recently discovered tremors (gold stars) and the location of the proposed stations, whose instrumentation will be used to study the behavior of faulting in the deep crust.
Project will monitor tremor activity beneath San Andreas Fault
December 9, 2010
UC Media Relations
by Robert Sanders
BERKELEY - The Berkeley Seismological Laboratory will begin early next year to install earthquake detectors on the southern San Andreas Fault near the town of Cholame to study mysterious tremors discovered beneath the area.
Tremors are extremely faint and periodic rumblings originating 20-40 kilometers below ground - far beneath the zone where earthquakes occur - that appear to be associated with slipping rocks deep in the earth.
UC Berkeley seismologists discovered the tremors in 2004 just south of the heavily instrumented Parkfield area of the fault, and subsequent studies suggest that changes in tremor activity may precede earthquakes. Tremors also have been detected in active earthquake zones in Japan and Washington state.
"The discovery of tremors deep in the roots of active plate boundary fault zones is arguably the most important discovery in earthquake science in decades," said Roland Bürgmann, principal investigator for the TremorScope project and professor and chair of UC Berkeley's Department of Earth and Planetary Science. "This is the first project in which a permanent instrument network has been specifically designed with tremor in mind."
TremorSCOPE: Imaging the Deep Workings of the San Andreas Fault
A project idea submitted for consideration by the Moore Foundation by the Berkeley Seismological Laboratory (Richard Allen, Pascal Audet, Roland Bürgmann, Doug Dreger, Peggy Hellweg; Bob Nadeau, Barbara Romanowicz, Taka'aki Taira)
Until recently, active fault zones were thought to deform via seismic earthquake slip in an upper brittle section of the crust, and by steady, aseismic shear below. However, in the last few years, this view has been shaken by seismological observations of seismic tremor deep in the roots of active fault zones.