%0 Journal Article %1 zhao_peng:2009 %A Zhao, Peng %A Peng, Zhigang %D 2009 %I Blackwell Publishing Ltd %J Geophysical Journal International %K geophysics seismology %N 3 %P 1817--1830 %R 10.1111/j.1365-246X.2009.04385.x %T Depth extent of damage zones around the central Calaveras fault from waveform analysis of repeating earthquakes %U http://dx.doi.org/10.1111/j.1365-246X.2009.04385.x %V 179 %X We systematically investigate spatial variations of temporal changes and depth extent of damage zones along the Calaveras fault that ruptured during the 1984 Morgan Hill earthquake by the waveform analysis of 333 sets of repeating earthquakes. We use a sliding window waveform cross-correlation technique to measure traveltime changes in waveforms generated by each repeating cluster. We find clear traveltime delays in the S- and early S-coda waves for events immediately after the Morgan Hill main shock. The amplitudes of the time delays decrease logarithmically with time since the main shock, indicating a time-dependent recovery (healing) process following the abrupt coseismic temporal changes. The largest temporal changes are observed at station CCO that is the closest to the rupture zone of the Morgan Hill main shock. The time delays at this station are larger for clusters in the top 6 km, and decrease systematically at larger depth. In comparison, the time delays observed at other five stations are much smaller, and do not show clear relationship with hypocentral depth. We suggest that the temporal changes at these five stations mostly occur in the top few hundred metres of the near-surface layers, while the temporal changes at station CCO are likely associated with the damage zone around the Calaveras fault that is well developed in the top few kilometres of the upper crust. Our results are consistent with the inference of a widespread damage and non-linearity in the near-surface layers associated with strong ground motions of nearby large earthquakes, and localized damages and flower-type structures around active faults based on previous studies of fault zone structures and recent 3-D numerical simulations.

@article{zhao_peng:2009, abstract = {We systematically investigate spatial variations of temporal changes and depth extent of damage zones along the Calaveras fault that ruptured during the 1984 Morgan Hill earthquake by the waveform analysis of 333 sets of repeating earthquakes. We use a sliding window waveform cross-correlation technique to measure traveltime changes in waveforms generated by each repeating cluster. We find clear traveltime delays in the S- and early S-coda waves for events immediately after the Morgan Hill main shock. The amplitudes of the time delays decrease logarithmically with time since the main shock, indicating a time-dependent recovery (healing) process following the abrupt coseismic temporal changes. The largest temporal changes are observed at station CCO that is the closest to the rupture zone of the Morgan Hill main shock. The time delays at this station are larger for clusters in the top 6 km, and decrease systematically at larger depth. In comparison, the time delays observed at other five stations are much smaller, and do not show clear relationship with hypocentral depth. We suggest that the temporal changes at these five stations mostly occur in the top few hundred metres of the near-surface layers, while the temporal changes at station CCO are likely associated with the damage zone around the Calaveras fault that is well developed in the top few kilometres of the upper crust. Our results are consistent with the inference of a widespread damage and non-linearity in the near-surface layers associated with strong ground motions of nearby large earthquakes, and localized damages and flower-type structures around active faults based on previous studies of fault zone structures and recent 3-D numerical simulations.}, added-at = {2012-09-01T13:08:21.000+0200}, author = {Zhao, Peng and Peng, Zhigang}, biburl = {https://www.bibsonomy.org/bibtex/2c773f7a375799487abfd78ce3ddd2017/nilsma}, doi = {10.1111/j.1365-246X.2009.04385.x}, interhash = {e88839d53623af59e338bf601e359461}, intrahash = {c773f7a375799487abfd78ce3ddd2017}, issn = {0956-540X}, journal = {Geophysical Journal International}, keywords = {geophysics seismology}, month = dec, number = 3, pages = {1817--1830}, publisher = {Blackwell Publishing Ltd}, timestamp = {2021-02-09T13:21:44.000+0100}, title = {Depth extent of damage zones around the central Calaveras fault from waveform analysis of repeating earthquakes}, url = {http://dx.doi.org/10.1111/j.1365-246X.2009.04385.x}, volume = 179, year = 2009 }