Creep is steady fault movement, varying from continuous
to episodic with creep events lasting minutes to days. Generally creep occurs
without any associated earthquake activity (i.e., aseismic.) Creep has been
monitored on the Hayward fault for forty years (Lienkaemper et al., 2001) and is also observed along some sections of other faults in the San
Francisco Bay region, including the San Andreas, Calaveras, Concord-Green Valley and Maacama (Galehouse and Lienkaemper, 2003.) Locations on the map showing creep evidence are indicated by green circles and given abbreviated descriptions.
MORE ABOUT CREEP:
1) Photos of creep effects.
2) Extended photographic tour of the Hayward fault.
3) Current alinement array data and much more about creep.
4) Alinement array data archive [Galehouse, 2002]
5) Creepmeters on Hayward fault and plot of 10 years of creepmeter data.
6) View USGS realtime creepmeter data plots.
DEEP CREEP AND EARTHQUAKES:
How deep does creep go? How can a creeping Hayward fault still produce major earthquakes?
The short answer is that the depth of creep varies, from as little 2 miles deep in northern Oakland to
as deep as 7 miles near the northern and southern ends of the fault. Unfortunately, this means the
lower, brittle fault zone remains largely locked (i.e., it's not creeping), so it's building strain
which can only be relieved by major earthquakes, which occur about every 100 to 200 years. The average
recurrence time for earthquakes is determined by paleoseismologists, geologists who work in trenches
across the faults. They document evidence of paleoearthquakes recorded in sedimentary layers, using radiocarbon analysis to date them.
For a comparison of scientific models of Hayward fault creep with depth: [Simpson et al., 2001.]
Hayward Fault Paleoseismology research papers:
1) [Hayward Fault Paleoearthquake Group, 1999]
2) [Lienkaemper et al., 2002]
3) [Lienkaemper et al., 2006]
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