Temporal changes in attenuation associated with the 2004 M6.0 Parkfield earthquake
Temporal changes in attenuation associated with the 2004 M6.0 Parkfield earthquake
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DOI：
10.1002/jgrb.50088
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发表时间：
2013-02-01
影响因子：
3.9
通讯作者：
Nadeau, R. M.
中科院分区：
文献类型：
--
作者：
Kelly, C. M.;Rietbrock, A.;Nadeau, R. M.
由于裂隙程度高，流体含量高，在断裂带中经常观察到地震衰减增加。然而，地震时衰减的时间变化很难受到约束，但可以给出骨折损伤和愈合的迹象。在这项研究中，计算了重复震群内地震之间的频谱比率，试图解决2004年帕克菲尔德6.0级地震时衰减的时间变化。地震后立即观察到衰减的急剧增加，然后在接下来的两年里衰减。研究了震级变化、时间窗长度和以前报道的震后速度变化对地震的影响。震后衰减用对数函数进行拟合。衰变的时间尺度与2004年帕克菲尔德6.0级地震后GPS数据和环境地震噪声速度的时间尺度相似。衰减变化的幅度对应于地震时Q(P)的大约10%的下降。最大的变化记录在断裂迹线的东北部，与北西向传播的破裂尖端后面的伸展象限的优先破坏一致。我们的分析表明，在同震破裂期间，地震衰减的显着变化以及由此导致的裂缝扩容仅限于深度小于5公里的范围内。引用：Kelly，C.M.，A.Rietbrock，D.R.Faulkner和R.M.Nadeau(2013)，与2004年Parkfield 6.0级地震相关的衰减的时间变化，J.GePhys。研究报告：Solid Earth，118630645，DOI：10.1002/jgrb.50088。
Elevated seismic attenuation is often observed in fault zones due to the high degree of fracturing and fluid content. However, temporal changes in attenuation at the time of an earthquake are poorly constrained but can give indications of fracture damage and healing. In this study, spectral ratios between earthquakes within repeating clusters are calculated in an attempt to resolve temporal variations in attenuation at the time of the 2004 M6.0 Parkfield earthquake. A sharp increase in attenuation is observed immediately after the earthquake, which then decays over the next 2 years. Influences of intercluster magnitude variations, time window length and previously reported postseismic velocity changes are investigated. The postseismic decay is fit by a logarithmic function. The timescale of the decay is found to be similar to that in GPS data and ambient seismic noise velocities following the 2004 M6.0 Parkfield earthquake. The amplitude of the attenuation change corresponds to a decrease of approximately 10% in Q(p) at the time of the earthquake. The greatest changes are recorded on the northeast of the fault trace, consistent with preferential damage in the extensional quadrant behind a north-westerly propagating rupture tip. Our analysis suggests that significant changes in seismic attenuation and hence fracture dilatancy during coseismic rupture are limited to depths of less than about 5 km. Citation: Kelly, C. M., A. Rietbrock, D. R. Faulkner, and R. M. Nadeau (2013), Temporal changes in attenuation associated with the 2004 M6.0 Parkfield earthquake, J. Geophys. Res. Solid Earth, 118, 630-645, doi:10.1002/jgrb.50088.