Spatial distribution of high-frequency energy radiation on the fault of the 1995 Hyogo-Ken Nanbu, Japan, earthquake (MW 6.9) on the basis of the seismogram envelope inversion
Spatial distribution of high-frequency energy radiation on the fault of the 1995 Hyogo-Ken Nanbu, Japan, earthquake (MW 6.9) on the basis of the seismogram envelope inversion
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DOI：
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发表时间：
1999-02
影响因子：
3
通讯作者：
H. Nakahara;H. Sato;M. Ohtake;T. Nishimura
中科院分区：
文献类型：
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作者：
H. Nakahara;H. Sato;M. Ohtake;T. Nishimura
摘要通过分析1995年日本神户兵古-南部（M W 6.9）地震主震和余震的地震记录包络，研究了高频（1 Hz以上）S波能量的产生和传播。我们首先研究了高频S波能量在震源周围非均质岩石圈中的传播特征。通过对余震记录的多次延时时间窗分析方法，我们估计了定量表征介质非均质性的两个参数：总散射系数和介质对S波的本征吸收。利用所得到的参数，利用辐射传递理论合成的包络格林函数，较好地再现了余震的观测包络。接下来，我们将包络反演方法应用于13个主震强震记录。将49 × 21 km的主震断层面划分为21个7 × 7 km平方的次级断层，估计了该断层面高频能量辐射的空间分布。通过网格搜索确定各次断层的平均恒定破裂速度和能量辐射持续时间分别为3.0 km/sec和5.0 sec。在4个频带中，全断层面辐射能量分别为4.9 × 10 14 J （1 ~ 2 Hz）、3.3 × 10 14 J （2 ~ 4 Hz）、1.5 × 10 14 J （4 ~ 8 Hz）、8.9 × 10 12 J （8 ~ 16 Hz）和9.8 × 10 14 J。我们发现，强能量主要从主震断层面上的三个区域辐射出来：初始破裂点周围、浅滩岛地表附近和神户地下的浅层部分。我们解释说，能量部分分别与破裂加速、断层表面破裂和破裂终止有关。
Abstract We studied the generation and propagation of high-frequency (above 1 Hz) S -wave energy from the 1995 Hyogo-Ken Nanbu (Kobe), Japan, earthquake ( M W 6.9) by analyzing seismogram envelopes of the mainshock and aftershocks. We first investigated the propagation characteristics of high-frequency S -wave energy in the heterogeneous lithosphere around the source region. By applying the multiple lapse time window analysis method to aftershock records, we estimated two parameters that quantitatively characterize the heterogeneity of the medium: the total scattering coefficient and the intrinsic absorption of the medium for S waves. Observed envelopes of aftershocks were well reproduced by the envelope Green functions synthesized based on the radiative transfer theory with the obtained parameters. Next, we applied the envelope inversion method to 13 strong-motion records of the mainshock. We divided the mainshock fault plane of 49 × 21 km into 21 subfaults of 7 × 7 km square and estimated the spatial distribution of the high-frequency energy radiation on that plane. The average constant rupture velocity and the duration of energy radiation for each subfault were determined by grid searching to be 3.0 km/sec and 5.0 sec, respectively. Energy radiated from the whole fault plane was estimated as 4.9 × 10 14 J for 1 to 2 Hz, 3.3 × 10 14 J for 2 to 4 Hz, 1.5 × 10 14 J for 4 to 8 Hz, 8.9 × 10 12 J for 8 to 16 Hz, and 9.8 × 10 14 J in all four frequency bands. We found that strong energy was mainly radiated from three regions on the mainshock fault plane: around the initial rupture point, near the surface at Awaji Island, and a shallow portion beneath Kobe. We interpret that energetic portions were associated with rupture acceleration, a fault surface break, and rupture termination, respectively.