We have developed a global earthquake monitoring system based on low-latency measurements from more than 1000 existing Global Navigational Satellite System (GNSS) receivers, of which nine captured the 2019 Mw 6.4 Ridgecrest, California, foreshock and Mw 7.1 mainshock earthquakes. For the foreshock, coseismic offsets of up to 10 cm are resolvable on one station closest to the fault, but did not trigger automatic offset detection. For the mainshock, GNSS monitoring determined its coseismic deformation of up to 70 cm on nine nearby stations within 25 s of event nucleation. These 25 s comprise the fault rupture duration itself (roughly 10 s of peak moment release), another 10 s for seismic waves and displacement to propagate to nearby GNSS stations, and a few additional seconds for surface waves and other crustal reverberations to dissipate sufficiently such that coseismic offset estimation filters could reconverge. Latency between data acquisition in the Mojave Desert and positioning in Washington State averaged 1.4 s, a small fraction of the fault rupture time itself. GNSS position waveforms for the two closest stations that show the largest dynamic and static displacements agree well with postprocessed time series. Mainshock coseismic ground deformation estimated within 25 s of origin time also agrees well with, but is ∼10% smaller than, deformation estimated using 48 hr observation windows, which may reflect rapid postseismic fault creep or the cumulative effect of nearly 1000 aftershocks in the 48 hr following the mainshock. GNSS position waveform shapes, which comprise a superposition of dynamic and static displacements, are well modeled by frequency–wavenumber synthetics for the Hadley–Kanamori 1D crustal structure model and the U.S. Geological Survey finite-rupture distribution and timing. These results show that GNSS seismic monitoring performed as designed and offers a newmeans of rapidly characterizing large earthquakes globally.

中文翻译：

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25 秒测定 2019 年 Mw 7.1 Ridgecrest 地震同震变形

我们开发了一个全球地震监测系统，该系统基于 1000 多个现有全球导航卫星系统 (GNSS) 接收器的低延迟测量，其中 9 个接收器捕获了 2019 年加利福尼亚州里奇克莱斯特的前震和 Mw 7.1 主震地震。对于前震，在离断层最近的一个台站上可以解决高达 10 厘米的同震偏移，但没有触发自动偏移检测。对于主震，GNSS 监测在事件成核后 25 秒内确定了其在附近 9 个站点上高达 70 厘米的同震变形。这 25 秒包括断层破裂持续时间本身（大约 10 秒的峰值力矩释放），另外 10 秒用于地震波和位移传播到附近的 GNSS 站，再过几秒钟让表面波和其他地壳混响充分消散，以便同震偏移估计滤波器可以重新收敛。莫哈韦沙漠的数据采集和华盛顿州的定位之间的延迟平均为 1.4 秒，这是断层破裂时间本身的一小部分。显示最大动态和静态位移的两个最近站点的 GNSS 位置波形与后处理时间序列非常吻合。在起源时间 25 s 内估计的主震同震地面变形也与使用 48 小时观测窗估计的变形非常吻合，但比使用 48 小时观测窗估计的变形小 10%，这可能反映了震后断层的快速蠕变或 48 年近 1000 次余震的累积效应。 hr 主震后。GNSS 位置波形形状，包括动态和静态位移的叠加，通过频率-波数合成对 Hadley-Kanamori 一维地壳结构模型和美国地质调查局有限破裂分布和时间进行了很好的建模。这些结果表明，GNSS 地震监测按设计进行，并提供了一种快速表征全球大地震的新方法。