Widespread fault creep in the northern San Francisco Bay Area revealed
by multi-station cluster detection of repeating earthquakes
Abstract
We search for repeating earthquakes (REs) in the northern San Francisco
Bay Area in 1984-2016. By comparing over 670,000 waveforms from
~75,000 events, we identify candidate clusters of events
whose waveforms have high cross-correlation coefficients at multiple
stations. A key difference with our approach is that these
‘multi-station clusters’ do not require each event in a family be
recorded at multiple common stations. We validate these candidate REs by
estimating precise relative relocations for the events in each cluster.
We identify 59 RE families whose relocated hypocenters are separated by
less than one source radius. These are distributed throughout the
Maacama fault zone, and along the northern Rodgers Creek and central
Bartlett Springs faults, implying that widespread, pervasive creep
occurs on those faults, at rates of 1-6 mm/yr. At either end of the
Maacama fault, the RE pattern highlights structural complexity,
suggesting that multiple subparallel strands may be active and creeping.