• ISSN 2097-1893
    • CN 10-1855/P

    火星单台震源机制研究进展

    Review of advances in Martian focal mechanisms

    • 摘要: 地震过程通常是岩质行星内部因应力长期积累而发生突然破裂和块体相对运动,并伴随能量释放的动力学过程. 研究其成因机制不仅有助于理解行星内部应力的积累与释放过程,还能揭示构造运动、岩浆活动等深部动力学过程. 已有探测证实,火星当前仍发生一定数量的火星震,其成因机制是研究火星内部动力过程的关键窗口. 震源机制参数(走向、倾角、滑动角)可直接反映深部的构造活动,是揭示火星震的触发机理的重要依据. 相较而言,地球上的震源机制反演方法通常依赖于多台站(台网)及良好的方位角覆盖,而火星“洞察”号单台观测对求解火星震的震源机制构成明显的技术挑战. 因此,系统评估现有方法的适用性,旨在为发展适用于单台观测条件下的震源机制反演策略提供研究参考. 本文梳理了基于初动极性振幅和波形拟合的地震震源机制反演方法;总结已有的基于单台数据的地震震源机制研究成果,并从方法角度介绍了火星震源机制研究现状. 通过上述综合回顾,旨在为单台观测的火星震源机制研究提供方法和技术研究思路启发.

       

      Abstract: Earthquakes represent dynamic processes in rocky planets where accumulated stress leads to sudden rupture, block movement, and energy release. Investigating their origin mechanisms not only advances our understanding of planetary stress accumulation and release, but also reveals deep dynamic processes, including tectonic activity and magmatism. Current research confirms ongoing seismic activity on Mars, providing a critical window into the planet's interior dynamics. The focal mechanism (strike, dip, and slip angles) directly reflects deep tectonic activity and serves as key evidence for understanding Marsquake triggering processes. While Earth focal mechanism inversion typically requires multi-station networks with good azimuthal coverage, Mars is currently limited to single-station data from InSight, posing significant technical challenges. The systematic evaluation of existing methods is crucial for developing novel inversion strategies for single-station observations. This study first reviews Earth-based focal mechanism methods, including those based on first-motion polarity, amplitude, and waveform fitting. Methods relying on first-motion polarity and amplitude require well-distributed station networks for complete focal mechanism sampling. For Mars' single-station inversion, P/S polarities and amplitude ratios alone cannot adequately constrain focal mechanisms. Waveform information must be fully utilized, with polarity/amplitude data typically incorporated into waveform-based inversions. The relative focal mechanism approach is suitable for analyzing clustered events-particularly relevant for Mars' regionally concentrated marsquakes. In waveform-based marsquake studies, velocity model uncertainties introduce challenges for full-waveform fitting. Seismic phase windowing with permitted time shifts during waveform modeling helps mitigate velocity model errors, making this approach (e.g. CAP) more viable for single-station inversions on Mars. Next, we summarize single-station inversion techniques (based on body waves, surface waves, full waveforms) developed for limited data on earth. Finally, we synthesize marsquake focal mechanism research, covering: 1) InSight mission background (instrumentation, data, Earth-Mars observational differences); 2) Tectonic setting (landing site, crust-mantle structure, stress field, thermal evolution); and 3) Research progress (methods, findings, unresolved challenges). In Mars focal mechanism studies, single-station waveform-fitting methods have been widely developed and applied, effectively addressing the insufficient sampling issue in single-station data. However, current results still exhibit significant uncertainties and inconsistencies across different studies, necessitating further optimization of inversion strategies. The clustered distribution of marsquakes enables the application of relative focal mechanism methods. Initial solutions obtained through waveform analysis can be further constrained using relative mechanism approaches. Earlier studies were limited by insufficient velocity structure and uncertain event locations, highlighting the need to update existing solutions using improved structural models and more accurate event locations. Through the comprehensive synthesis, we aim to provide methodological and theoretical support for single-station-based Marsquake focal mechanism research.

       

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