Since February 2019, NASA's InSight lander is recording seismic signals on the planet Mars, which, for the first time, allows to observe ongoing tectonic processes with geophysical methods. A number of Marsquakes have been located in the Cerberus Fossae graben system in Elysium Planitia and further west, in the Orcus Patera depression. We present a first study of the focal mechanisms of three well‐recorded events (S0173a, S0183a, S0235b) to determine the processes dominating in the source region. We infer for all three events a predominantly extensional setting. Our method is adapted to the case of a single, multicomponent receiver and based on fitting waveforms of P and S waves against synthetic seismograms computed for the initial crustal velocity model derived by the InSight team. We explore the uncertainty due to the single‐station limitation and find that even data recorded by one station constrains the mechanisms (reasonably) well. For the events in the Cerberus Fossae region (S0173a, S0235b) normal faulting with a relatively steep dipping fault plane is inferred, suggesting an extensional regime mainly oriented E‐W to NE‐SW. The fault regime in the Orcus Patera region is not determined uniquely because only the P wave can be used for the source inversion. However, we find that the P and weak S waves of the S0183a event show similar polarities to the event S0173, which indicates similar fault regimes.

中文翻译：

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地震的首要震源机制

自2019年2月以来，NASA的InSight着陆器正在记录火星上的地震信号，这是首次允许使用地球物理方法观察正在进行的构造过程。在Elysium Planitia和更西边的Orcus Patera凹陷的Cerberus Fossae en住系统中，已经发生了许多地震。我们目前对三个记录良好的事件（S0173a，S0183a，S0235b）的焦点机制进行初步研究，以确定在源区中占主导地位的过程。对于这三个事件，我们推断一个主要是可扩展的设置。我们的方法适用于单个多分量接收器的情况，并基于P和S的拟合波形InSight团队为初始地壳速度模型计算出的地震波对合成地震图的反演。由于单站的局限性，我们探索了不确定性，发现即使一个站记录的数据也很好地约束了这种机制。对于Cerberus Fossae地区（S0173a，S0235b）的事件，可以推断出具有相对陡峭的倾斜断层的正常断层，暗示了一种以E-W向NE-SW为主的扩展体系。由于只有P波可用于震源反演，因此不能唯一确定Orcus Patera地区的断层状态。但是，我们发现S0183a事件的P波和弱S波显示与事件S0173相似的极性，这表明相似的断层状态。