HR: 1340h
AN: S13B-0191    [Abstracts]
TI: Nature of Repeating Earthquake Sequence: Observations From the Chihshang Fault of Eastern Taiwan
AU: * Rau, R
EM: raurj@mail.ncku.edu.tw
AF: Department of Earth Sciences, National Cheng Kung University, Tainan, 701 Taiwan
AU: Chen, H
EM: l4890102@mail.ncku.edu.tw
AF: Department of Earth Sciences, National Cheng Kung University, Tainan, 701 Taiwan
AU: Nadeau, R
EM: nadeau@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, University of California, Berkeley, Berkeley, CA 94720-4760 United States
AB: Regularity of earthquake recurrence and sizes of repeated ruptures depend on changes in strain rate and frictional parameters from numerical and laboratory studies. In nature, the factors controlling the regularity of earthquake recurrence become much more complicated and are not well understood because of limited observations of repeatedly ruptured sources. Forty-five repeating micro-earthquake sequences observed on the creeping Chihshang fault in eastern Taiwan offer a great opportunity that may answer such a question. The Chihshang fault repeating earthquake sequences with local magnitudes of 2.1 ~ 3.8 and recurrence intervals of a few seconds to 6.7 years are classified into three groups, they are quasi-periodic, aperiodic, and triggering types, independently, based on their occurrence lifetime, regularity in recurrence time, and variation in source size. We estimated the spatial separation between two repeating sequences, namely inter-asperity distance, and calculated the time difference between the temporally neighboring repeating events in two different repeating sequences to discern their temporal correlation. We found that the quasi-periodic and aperiodic repeaters have distinct behavior in both inter-asperity distance and the broadness of earthquake size distribution. Quasi-periodic repeaters tend to have larger inter-asperity distance and smaller range of size distribution. Furthermore, when the inter-asperity distance is less than 5-km, the quasi-periodic repeaters have weaker temporal correlation with each other than the aperiodic repeaters. It indicates that the occurrence of aperiodic repeaters is more apt to be affected by nearby repeaters especially when the repeaters are located close to each other. We suggest that the quasi-periodic sequences may be more isolated in space and stronger in material strength. The repeating earthquakes observed from other regions such as California, Japan, and Tonga indicate that in the areas where the quasi-periodic repeaters were observed, the mean size-difference in repeaters is smaller than the areas found to have aperiodic repeaters only. Such feature is similar with the repeating behavior revealed from the Chihshang repeating sequences. In addition, larger degree of periodicity leads to smaller magnitude difference in a sequence. It leads to the conclusion that the relationship between the regularity of repeat time and size difference in a repeating sequence is evident not only in the Chihshang fault but also in other regions, indicating the repeating behavior may follow a universal rule.
DE: 7209 Earthquake dynamics (1242)
DE: 7215 Earthquake source observations (1240)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 8118 Dynamics and mechanics of faulting (8004)
DE: 8150 Plate boundary: general (3040)
SC: Seismology [S]
MN: Fall Meeting 2005