response of the san jacinto fault zone to static stress changes from the 1992 landers earthquake
DESCRIPTION
Response of the San Jacinto fault zone to static stress changes from the 1992 Landers earthquake. M. Nic Bhloscaidh and J. McCloskey School of Environmental Sciences, University of Ulster C. J. Bean School of Geological Sciences, University College Dublin. Coulomb stresses and aftershocks. - PowerPoint PPT PresentationTRANSCRIPT
Response of the San Jacinto fault zone to static stress changes from the 1992 Landers earthquake
M. Nic Bhloscaidh and J. McCloskey School of Environmental Sciences, University of Ulster
C. J. BeanSchool of Geological Sciences, University College Dublin
Coulomb stresses and aftershocks
Landers sequenceSouthern California, 1992
CFS
San Jacinto Fault Zone
San Andreas Fault Zone M6.1 Joshua Tree23rd April 1992
M7.3 Landers28th June 1992
M7.1 Hector Mine16th October 1999
20km
M6.5 Big Bear28th June 1992
California Geological Survey
The 1992 Landers earthquake sequence
Landers pre-seismicity
R – aftershock rater – pre-seismicity rate
Mallman and Zoback (2005)
Changes in rate after Landers
The San Jacinto Fault Zone
SAN BERNARDINO
SAN JACINTO
ANZA
Sanders and Kanamori (1984)
Coulomb Stress Triggering CFSln rR
0CFS
0ln rR
0CFS
0ln rR
0CFS
0ln rR
Correlation between rate changes and static stress changes
San Bernardino
San JacintoAnza
6.578.0
The Coulomb Rate-State model
AreR /CFS)0(
ACFS
rR
)0(ln
attA eertR //CFS )1(1
)(
]CFS)1ln([)( //CFS atTA eeArTN
Dieterich, 1994
Estimating the parameters of the CRS model
bars4.0A
years8at
Conclusions
We find a statistically significant positive correlation between the change in rate and the magnitude of the Coulomb stress change, with a correlation coefficient of 0.76 (5.6σ).
This result is an important step in the validation of Coulomb stress based methods for quantitative seismicity forecasting.
The correspondence between Coulomb stress changes and observed rate changes is sensitive to strong heterogeneity in aftershock locations and orientations associated with the presence of large-scale structure in aftershock study areas.
Where the regional structure is mapped, incorporating it explicitly into Coulomb stress models may improve the performance of quantitative Coulomb stress based forecasts.