The slip history of the 1994 Northridge, California, earthquake determined from strong-motion, teleseismic, GPS, and leveling data
The slip history of the 1994 Northridge, California, earthquake determined from strong-motion, teleseismic, GPS, and leveling data
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DOI：
10.1785/bssa08601b0s49
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发表时间：
1996-02
影响因子：
3
通讯作者：
D. Wald;T. Heaton;K. Hudnut
中科院分区：
文献类型：
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作者：
D. Wald;T. Heaton;K. Hudnut
我们提出了一个破裂模型北岭地震，确定从联合反演的近源强地面运动记录，P和SH地震体波，全球定位系统（GPS）位移矢量，和永久隆起测量沿着水准线。该断层被定义为走向122°，倾向西南偏南40°。测得平均前倾角为101°，平均滑动量为1.3m，最大滑动量约为3 m。我们估计的地震矩为1.3 ± 0.2 × 1026达因-厘米（效力为0.4公里3）。破裂区域相对于整个余震的规模来说很小，沿走向约为沿着15 km，沿倾向方向约为20 km，并且没有滑动浅于约5至6 km的迹象。向上倾斜的强震速度波形主要由震源方向性引起的大S波脉冲所控制，并由至少2至3个不同的到达波（相隔几秒）组成。在南方位的台站显示两个主要的S波到达时间间隔较长（约4至5秒）。这些观测结果最好用子事件的复杂分布来模拟：最初的S波到达来自一个粗糙体，该粗糙体始于震源，向上倾斜延伸，并向北延伸，第二个较大的子事件集中在那里（约12公里远）。南方位的次级S波与震源以西8 km处19 km深度的另一个高滑区的附加能量辐射最吻合。个别数据集的分辨能力进行检查，通过预测的大地测量（GPS和水准测量）位移与从波形数据确定的位错模型，反之亦然，也通过分析如何以及EQUEENCY的解决方案预测记录的强烈运动。大地位移的一般特征不能很好地从独立于强震数据确定的模型中预测出来;同样，从大地数据确定的滑动模型也不能充分再现强震特征。而一个特别平滑的滑动模式是足以满足大地测量数据，强震和地震数据需要一个更不均匀的滑动分布，以重现速度振幅和频率的内容。虽然地球物理模型可以充分再现强震速度记录的整体振幅和频率内容，但它在预测大地测量数据方面做得很差。因此，一个强大的代表性的滑动历史和异质性需要这些数据集的综合分析。
We present a rupture model of the Northridge earthquake, determined from the joint inversion of near-source strong ground motion recordings, P and SH teleseismic body waves, Global Positioning System (GPS) displacement vectors, and permanent uplift measured along leveling lines. The fault is defined to strike 122° and dip 40° to the south-southwest. The average rake vector is determined to be 101°, and average slip is 1.3 m; the peak slip reaches about 3 m. Our estimate of the seismic moment is 1.3 ± 0.2 × 1026 dyne-cm (potency of 0.4 km3). The rupture area is small relative to the overall aftershock dimensions and is approximately 15 km along strike, nearly 20 km in the dip direction, and there is no indication of slip shallower than about 5 to 6 km. The up-dip, strong-motion velocity waveforms are dominated by large S-wave pulses attributed to source directivity and are comprised of at least 2 to 3 distinct arrivals (a few seconds apart). Stations at southern azimuths indicate two main S-wave arrivals separated longer in time (about 4 to 5 sec). These observations are best modeled with a complex distribution of subevents: The initial S-wave arrival comes from an asperity that begins at the hypocenter and extends up-dip and to the north where a second, larger subevent is centered (about 12 km away). The secondary S arrivals at southern azimuths are best fit with additional energy radiation from another high slip region at a depth of 19 km, 8 km west of the hypocenter. The resolving power of the individual data sets is examined by predicting the geodetic (GPS and leveling) displacements with the dislocation model determined from the waveform data, and vice versa, and also by analyzing how well the teleseismic solution predicts the recorded strong motions. The general features of the geodetic displacements are not well predicted from the model determined independently from the strong-motion data; likewise, the slip model determined from geodetic data does not adequately reproduce the strong-motion characteristics. Whereas a particularly smooth slip pattern is sufficient to satisfy the geodetic data, the strong-motion and teleseismic data require a more heterogeneous slip distribution in order to reproduce the velocity amplitudes and frequency content. Although the teleseismic model can adequately reproduce the overall amplitude and frequency content of the strong-motion velocity recordings, it does a poor job of predicting the geodetic data. Consequently, a robust representation of the slip history and heterogeneity requires a combined analysis of these data sets.