Determination of earthquake energy release and ML using TERRAscope
Determination of earthquake energy release and ML using TERRAscope
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使用 TERRAscope 确定地震能量释放和 ML
DOI：
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
L. Jones
中科院分区：
文献类型：
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作者：
H. Kanamori;J. Mori;E. Hauksson;T. Heaton;L. Hutton;L. Jones
我们使用 TERRAscope 的大规模超宽带记录估算了南加州地震辐射的能量。我们使用的方法涉及地面运动速度平方的时间积分以及距离衰减函数和台站修正的经验确定。时间积分通常在 P 波到达后 2 分钟的持续时间内进行。我们获得的能量积分的衰减曲线由 q(r) = cr^(−n)exp(−kr)(r^2 = Δ^2 + h_(ref)^2) 给出，其中 c = 0.49710、n = 1.0322、k = 0.0035 km^(−1) 和 h_(ref) = 8 km，其中 Δ 是震中距离。使用 TERRAscope 数据采用类似的方法确定 M_L。确定 M_L 的台站修正，使得 TERRAscope 确定的 M_L 值与传统光学伍德-安德森地震仪确定的 M_L 值一致。对于 1.5 6.5，M_L 饱和。比率 E_S/M_0（M_0：地震矩）是六次地震平均应力降的量度：1989 年蒙特贝罗地震 (M_L = 4.6)、1989 年帕萨迪纳地震 (M_L = 4.9)、1990 年高地地震 (M_L = 5.2)、1991 年马德雷山脉地震 (M_L = 5.8)、 1992 年约书亚树地震（M_L = 6.1）和 1992 年兰德斯地震（M_w = 7.3）大约比其他地震（包括 1987 年惠蒂尔海峡地震、马德雷山脉地震、约书亚树地震和圣哈辛托断层上的两次地震）的余震大 10 倍。主震与其大余震之间的应力降差异可能类似于长、短重复时间断层上的地震之间的应力降差异。余震发生在主震滑移发生的断层面上，其愈合时间很短，因此应力降较低。据信，南加州横断山脉的锋断层系统发生大地震的重复时间很长，可达几千年。因此，横向山脉中的事件可能比重复时间较短的断层（例如圣安德烈亚斯断层和圣哈辛托断层）上发生的事件具有更高的应力降。横向山脉和洛杉矶盆地发生极高应力降事件的观察结果对区域地震潜力具有重要意义。这些高应力降事件在发震带底部附近的发生强烈表明这些断层系统能够支撑最终在重大地震事件中释放的高应力。使用宽带数据根据 E_S/M_0 比来描述地震特征将有助于描绘洛杉矶盆地和横向山脉中发震应力的空间分布。
We estimated the energy radiated by earthquakes in southern California using on-scale very broadband recordings from TERRAscope. The method we used involves time integration of the squared ground-motion velocity and empirical determination of the distance attenuation function and the station corrections. The time integral is typically taken over a duration of 2 min after the P-wave arrival. The attenuation curve for the energy integral we obtained is given by q(r) = cr^(−n)exp(−kr)(r^2 = Δ^2 + h_(ref)^2) with c = 0.49710, n = 1.0322, k = 0.0035 km^(−1), and h_(ref) = 8 km, where Δ is the epicentral distance. A similar method was used to determine M_L using TERRAscope data. The station corrections for M_L are determined such that the M_L values determined from TERRAscope agree with those from the traditional optical Wood-Anderson seismographs. For 1.5 6.5, M_L saturates. The ratio E_S/M_0 (M_0: seismic moment), a measure of the average stress drop, for six earthquakes, the 1989 Montebello earthquake (M_L = 4.6), the 1989 Pasadena earthquake (M_L = 4.9), the 1990 Upland earthquake (M_L = 5.2), the 1991 Sierra Madre earthquake (M_L = 5.8), the 1992 Joshua Tree earthquake (M_L = 6.1), and the 1992 Landers earthquake (M_w = 7.3), are about 10 times larger than those of the others that include the aftershocks of the 1987 Whittier Narrows earthquake, the Sierra Madre earthquake, the Joshua Tree earthquake, and the two earthquakes on the San Jacinto fault. The difference in the stress drop between the mainshock and their large aftershocks may be similar to that between earthquakes on a fault with long and short repeat times. The aftershocks, which occurred on the fault plane where the mainshock slippage occurred, had a very short time to heal, hence a low stress drop. The repeat time of the major earthquakes on the frontal fault systems in the Transverse Ranges in southern California is believed to be very long, a few thousand years. Hence, the events in the Transverse Ranges may have higher stress drops than those of the events occurring on faults with shorter repeat times, such as the San Andreas fault and the San Jacinto fault. The observation that very high stress-drop events occur in the Transverse Ranges and the Los Angeles Basin has important implications for the regional seismic potential. The occurrence of these high stress-drop events near the bottom of the seismogenic zone strongly suggests that these fault systems are capable of supporting high stress that will eventually be released in major seismic events. Characterization of earthquakes in terms of the E_S/M_0 ratio using broadband data will help delineate the spatial distribution of seismogenic stresses in the Los Angeles basin and the Transverse Ranges.