Spatiotemporal distribution of seismic energy radiation from low-frequency tremor in western Shikoku, Japan
Spatiotemporal distribution of seismic energy radiation from low-frequency tremor in western Shikoku, Japan
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DOI：
10.1029/2008jb006043
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发表时间：
2009-10-21
影响因子：
3.9
通讯作者：
Obara, Kazushige
中科院分区：
文献类型：
--
作者：
Maeda, Takuto;Obara, Kazushige
本文估计了日本四国西部慢滑事件相关低频震颤辐射地震能量的时空格局。利用在Hi-net站点观测到的包络相关性的空间衰减均方振幅和差分走时测量来定位地震并估计其地震能量。用尾数归一化方法对震源放大因子进行了校正。震颤的位置被估计为观测到的能量衰减和差分传播时间都得到很好解释的位置。总能量释放的时间模式与观测到的倾斜记录非常吻合。虽然四国西部6次慢滑事件的能量辐射空间格局差异较大，但它们重叠的区域总是辐射出相对较高的能量水平。在2 ~ 10hz带宽范围内，地震的估计带限能量率通常在10(5)~ 10(6)J/min之间，尽管辐射能量存在时间变化。5.9 ~ 6.1级强震在8 ~ 13天的持续时间内释放的总能量约为10(8)J。与伴随的SSE的瞬间释放相比，这是相当小的能量辐射。慢滑极低频地震的标度能量，即地震矩与地震能量之比，估计比普通地震小5个数量级。
The spatiotemporal patterns of the radiated seismic energy from low-frequency tremor associated with slow slip events in western Shikoku, Japan, have been estimated. A spatially decaying mean square amplitude and differential traveltime measurement from envelope correlations observed at Hi-net stations were used to locate tremors and to estimate their seismic energies. Tremor amplitude was corrected for the site amplification factors estimated using the coda normalization method. The location of the tremor is estimated as the position where both the decay of the observed energy and the differential travel times are well explained. The temporal pattern of the total energy released agrees very well with the observed tilt records. Although the spatial patterns of the energy radiation vary strongly among the six slow slip events (SSEs) in western Shikoku, the region where they overlap always radiates relatively high levels of energy. The estimated band-limited energy rate of the tremor for a 2 to 10 Hz bandwidth was typically between 10(5) and 10(6) J/min, though there is temporal variation of the radiation energy. The released total energy associated with the SSEs whose magnitude is 5.9-6.1 is on the order of 10(8) J within the duration of SSEs of 8-13 days. This is quite small energy radiation compared to the moment release of accompanying SSE. The scaled energy, which is the ratio of the seismic moment and the seismic energy, for the slow slip and a very low frequency earthquake was estimated to be 5 orders of magnitude smaller than that of a regular earthquake.