The seismicity pattern along the San Andreas fault near Parkfield
and Cholame, California, varies distinctly over a length of only
fifty kilometres. Within the brittle crust, the presence of frictionally
weak minerals, fault-weakening high fluid pressures and chemical
weakening are considered possible causes of an anomalously weak fault
northwest of Parkfield. Non-volcanic tremor from lower-crustal and
upper-mantle depths is most pronounced about thirty kilometres southeast
of Parkfield and is thought to be associated with high pore-fluid
pressures at depth. Here we present geophysical evidence of fluids
migrating into the creeping section of the San Andreas fault that
seem to originate in the region of the uppermost mantle that also
stimulates tremor, and evidence that along-strike variations in tremor
activity and amplitude are related to strength variations in the
lower crust and upper mantle. Interconnected fluids can explain a
deep zone of anomalously low electrical resistivity that has been
imaged by magnetotelluric data southwest of the Parkfield-Cholame
segment. Near Cholame, where fluids seem to be trapped below a high-resistivity
cap, tremor concentrates adjacent to the inferred fluids within a
mechanically strong zone of high resistivity. By contrast, subvertical
zones of low resistivity breach the entire crust near the drill hole
of the San Andreas Fault Observatory at Depth, northwest of Parkfield,
and imply pathways for deep fluids into the eastern fault block,
coincident with a mechanically weak crust and the lower tremor amplitudes
in the lower crust. Fluid influx to the fault system is consistent
with hypotheses of fault-weakening high fluid pressures in the brittle
crust.
%0 Journal Article
%1 becken_etal:2011
%A Becken, Michael
%A Ritter, Oliver
%A Bedrosian, Paul A.
%A Weckmann, Ute
%D 2011
%I Nature Publishing Group
%J Nature
%K geophysics
%N 7375
%P 87--90
%R 10.1038/nature10609
%T Correlation between deep fluids, tremor and creep along the central
San Andreas fault
%U http://dx.doi.org/10.1038/nature10609
%V 480
%X The seismicity pattern along the San Andreas fault near Parkfield
and Cholame, California, varies distinctly over a length of only
fifty kilometres. Within the brittle crust, the presence of frictionally
weak minerals, fault-weakening high fluid pressures and chemical
weakening are considered possible causes of an anomalously weak fault
northwest of Parkfield. Non-volcanic tremor from lower-crustal and
upper-mantle depths is most pronounced about thirty kilometres southeast
of Parkfield and is thought to be associated with high pore-fluid
pressures at depth. Here we present geophysical evidence of fluids
migrating into the creeping section of the San Andreas fault that
seem to originate in the region of the uppermost mantle that also
stimulates tremor, and evidence that along-strike variations in tremor
activity and amplitude are related to strength variations in the
lower crust and upper mantle. Interconnected fluids can explain a
deep zone of anomalously low electrical resistivity that has been
imaged by magnetotelluric data southwest of the Parkfield-Cholame
segment. Near Cholame, where fluids seem to be trapped below a high-resistivity
cap, tremor concentrates adjacent to the inferred fluids within a
mechanically strong zone of high resistivity. By contrast, subvertical
zones of low resistivity breach the entire crust near the drill hole
of the San Andreas Fault Observatory at Depth, northwest of Parkfield,
and imply pathways for deep fluids into the eastern fault block,
coincident with a mechanically weak crust and the lower tremor amplitudes
in the lower crust. Fluid influx to the fault system is consistent
with hypotheses of fault-weakening high fluid pressures in the brittle
crust.
@article{becken_etal:2011,
abstract = {The seismicity pattern along the San Andreas fault near Parkfield
and Cholame, California, varies distinctly over a length of only
fifty kilometres. Within the brittle crust, the presence of frictionally
weak minerals, fault-weakening high fluid pressures and chemical
weakening are considered possible causes of an anomalously weak fault
northwest of Parkfield. Non-volcanic tremor from lower-crustal and
upper-mantle depths is most pronounced about thirty kilometres southeast
of Parkfield and is thought to be associated with high pore-fluid
pressures at depth. Here we present geophysical evidence of fluids
migrating into the creeping section of the San Andreas fault that
seem to originate in the region of the uppermost mantle that also
stimulates tremor, and evidence that along-strike variations in tremor
activity and amplitude are related to strength variations in the
lower crust and upper mantle. Interconnected fluids can explain a
deep zone of anomalously low electrical resistivity that has been
imaged by magnetotelluric data southwest of the Parkfield-Cholame
segment. Near Cholame, where fluids seem to be trapped below a high-resistivity
cap, tremor concentrates adjacent to the inferred fluids within a
mechanically strong zone of high resistivity. By contrast, subvertical
zones of low resistivity breach the entire crust near the drill hole
of the San Andreas Fault Observatory at Depth, northwest of Parkfield,
and imply pathways for deep fluids into the eastern fault block,
coincident with a mechanically weak crust and the lower tremor amplitudes
in the lower crust. Fluid influx to the fault system is consistent
with hypotheses of fault-weakening high fluid pressures in the brittle
crust.},
added-at = {2012-09-01T13:08:21.000+0200},
author = {Becken, Michael and Ritter, Oliver and Bedrosian, Paul A. and Weckmann, Ute},
biburl = {https://www.bibsonomy.org/bibtex/27f3ac026b9c3282d2511ec7e102563c6/nilsma},
day = 30,
doi = {10.1038/nature10609},
interhash = {a99ec7a7469be3858b6863fc9ec9035a},
intrahash = {7f3ac026b9c3282d2511ec7e102563c6},
issn = {0028-0836},
journal = {Nature},
keywords = {geophysics},
month = nov,
number = 7375,
pages = {87--90},
publisher = {Nature Publishing Group},
timestamp = {2021-02-09T13:24:39.000+0100},
title = {Correlation between deep fluids, tremor and creep along the central
San Andreas fault},
url = {http://dx.doi.org/10.1038/nature10609},
volume = 480,
year = 2011
}