Since landing in late 2018, the InSight lander has been recording seismic signals on the surface of Mars. Despite nominal prelanding estimates of one to three meteorite impacts detected per Earth year, none have yet been identified seismically. To inform revised detectability estimates, we simulated numerically a suite of small impacts onto Martian regolith and characterized their seismic source properties. For the impactor size and velocity range most relevant for InSight, crater diameters are 1–30 m. We found that in this range scalar seismic moment is 10⁶–10¹⁰ Nm and increases almost linearly with impact momentum. The ratio of horizontal to vertical seismic moment tensor components is ∼1, implying an almost isotropic P wave source, for vertical impacts. Seismic efficiencies are ∼10⁻⁶, dependent on the target crushing strength and impact velocity. Our predictions of relatively low seismic efficiency and seismic moment suggest that meteorite impact detectability on Mars is lower than previously assumed. Detection chances are best for impacts forming craters of diameter >10 m.

中文翻译：

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小撞击火星的地震矩和地震效率。

自2018年底登陆以来，InSight着陆器一直在火星表面记录地震信号。尽管名义上的着陆估计是每个地球年探测到1-3个陨石撞击，但尚无地震识别。为了提供修改后的可探测性估计值，我们通过数值模拟了一系列对火星重石的小影响，并对它们的震源特性进行了表征。对于与InSight最相关的冲击器尺寸和速度范围，弹坑直径为1–30 m。我们发现，在此范围内，标量地震矩为10 ⁶ – 10 ¹⁰  Nm，并且几乎随冲击动量线性增加。水平与垂直地震矩张量之比约为1，这意味着几乎各向同性P 波源，用于垂直冲击。取决于目标的抗压强度和冲击速度，抗震效率约为10 ^-6。我们对相对较低的地震效率和地震矩的预测表明，陨石撞击火星的可探测性低于先前的假设。检测机会最适合形成直径> 10 m的弹坑。