Moment-Duration Scaling of Low-Frequency Earthquakes in Guerrero, Mexico
Moment-Duration Scaling of Low-Frequency Earthquakes in Guerrero, Mexico
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DOI：
10.1029/2019jb019099
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发表时间：
2020-08-01
影响因子：
3.9
通讯作者：
Frank, William B.
中科院分区：
文献类型：
--
作者：
Farge, Gaspard;Shapiro, Nikolai M.;Frank, William B.
低频地震（LFE）是在震颤中检测到的，作为小的，重复的，脉冲的低频（1-8Hz）信号。虽然导致其信号的高频内容的这种损耗的机制仍有争议，但这一特征可能表明LFE起源处的震源过程与常规地震的震源过程不同。LFE产生的物理机制的关键约束可以通过建立它们的地震矩和源持续时间之间的标度律来获得。在这里，我们应用一个简单的频谱分析方法的S波形的LFE从格雷罗，墨西哥，测量他们的地震矩和拐角频率，代理源持续时间。我们发现M-0的特征值类似于3 × 10（12）N.m（M-w类似于2.3），f（c）类似于3.0 Hz，拐角频率对地震矩的依赖性很弱。墨西哥LFEs观测到的这一时刻-持续时间标度与以前在卡斯卡迪亚报道的相似，与常规地震的既定标度非常不同。这表明它们可以由几乎恒定大小的源产生，强度变化很大。低频地震并不表现出常规地震的自相似性特征，这表明它们起源的物理机制可能是本质上不同的。简明语言摘要低频地震是在板块边界断层的深部探测到的不寻常的小地震。它们发生在缓慢滑动的时期，当板块开始相互滑动时，速度比地震慢得多，但足够长的时间来释放可能导致大地震的能量。因此，它们携带了有关慢滑活跃时故障行为的宝贵信息。在这项研究中，我们分析了一个选择的低频地震从墨西哥俯冲的慢滑带，下面的格雷罗州。我们发现，它们的震级平均高于其他已被探测到的区域（M（w）1.5 - 3）。我们还发现，无论这些事件的大小，它们总是持续约0.3秒。相反，常规地震在规模增大时持续时间更长，日本南海的低频地震似乎也有类似的表现。我们讨论了一个物理机制，解释这种差异与定期地震和这种强烈的区域变化。地壳流体在极高压力下在板块之间循环的含义可能是这一机制的关键组成部分之一，因为它通常是缓慢的滑动过程。
Low-frequency earthquakes (LFEs) are detected within tremor, as small, repetitive, impulsive low-frequency (1-8Hz) signals. While the mechanism causing this depletion of the high-frequency content of their signal is still debated, this feature may indicate that the source processes at the origin of LFEs are different from those for regular earthquakes. Key constraints on the LFE-generating physical mechanisms can be obtained by establishing scaling laws between their seismic moment and source durations. Here we apply a simple spectral analysis method to the S waveforms of LFEs from Guerrero, Mexico, to measure their seismic moments and corner frequencies, a proxy to source duration. We find characteristic values of M-0 similar to 3x10(12) N.m (M-w similar to 2.3 ) and f(c)similar to 3.0 Hz with the corner frequency very weakly dependent on the seismic moment. This moment-duration scaling observed for Mexican LFEs is similar to one previously reported in Cascadia and is very different from the established one for regular earthquakes. This suggests that they could be generated by sources of nearly constant size with strongly varying intensities. LFEs do not exhibit the self-similarity characteristic of regular earthquakes, suggesting that the physical mechanisms at their origin could be intrinsically different.Plain Language Summary Low-frequency earthquakes are unusual, small earthquakes that are detected on the deep end of plate boundary faults. They occur during periods of slow slip, when the plates start sliding against each other much slower than during earthquakes, but long enough to release the energy that might otherwise have caused large earthquakes. Thus, they carry precious information about the fault behavior while slow slip is active. In this study, we analyze a selection of low-frequency earthquakes from a slow slip zone of the Mexican subduction, beneath the state of Guerrero. We find that their magnitude is on average higher than in other regions where they have been detected (M(w)1.5 - 3). We also find that whatever the magnitude of these events, they always last about 0.3 s. On the contrary, regular earthquakes are known to last longer when they grow larger, and low-frequency earthquakes in Nankai (Japan) appear to behave similarly. We discuss a physical mechanism explaining such a discrepancy with regular earthquakes and such strong regional variations. The implication of crustal fluids circulating at extremely high pressure in between plates might be one of the key components of this mechanism, as it often is for slow slip processes.