Brittle-Ductile Interactions in California
Brittle-Ductile Interactions in California
Credit:
K. Aki, A. Jin, V. Keilis-Borok, Z. Liu, I. Zaliapin/IRIS Consortium
Description
The figure illustrates the brittle-ductile correlation analysis in California, 1940-2003. Horizontal axis represents time, vertical axis represents scale of correlation. Blue area depicts scale-time where the brittle and ductile layers were correlated; pink areas where they were uncorrelated. As suggested by Aki’s Brittle-Ductile Interaction Hypothesis, the correlation is destroyed at progressively larger scales as a large regional earthquake approaches. The destruction of correlation at scales larger than 6 years is only observed a couple of years prior to the Loma Prieta and San Simeon earthquakes.
This paper introduces a statistical technique, based on the recently developed Multiscale Trend Analysis (MTA), for quantifying correlations between non-stationary processes observed at irregular non-coincident time grids. We apply this technique to studying the temporal correlation between the dynamics of the ductile and brittle layers in the lithosphere using seismicity of California during 1940-2003. Our results confirm the previously reported strong positive correlation between the coda Q-1 and seismicity and its drop before major earthquakes observed in California. The proposed technique has significant advantages over the conventional correlation analysis: (1) MTA allows one to work directly with non-coincident time series without preliminary resampling the data; (2) The correlation is defined via the stable objects --- trends --- rather than noisy individual observations, hence it is highly robust; (3) The correlations are quantified at different time scales. The suggested technique seems promising for the wide range of applied problems dealing with coupled time series.
Jin A., Aki K., Liu Z., Keilis-Borok V. I., Seismological evidence for the brittle-ductile interaction hypothesis on earthquake loading, Earth Planets and Space, 56 (8), 823-830, 2004.
Zaliapin, I., Jin, A., Liu, Z., Aki, K., and Keilis-Borok V., Temporal (un)correlations between coda Q-1 and seismicity – Multiscale Trend Analysis, Pure. Appl. Geophys., 162, 827-841, 2005.
K. Aki • La Plaine des Cafres, France
A. Jin • National Research Institute for Earth Sciences and Disaster Prevention, Tsukuba, Ibaraki, Japan
V. Keilis-Borok, Z. Liu, I. Zaliapin • University of California, Los Angeles
Photographer / Contributor: K. Aki, A. Jin, V. Keilis-Borok, Z. Liu, I. Zaliapin
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