GROUND MOTION ESTIMATION FOR THE LARGEST RECORDED INSIGHT EVENT

Based on Insight Mission’s seismic recordings, Martian seismology primarily focuses on exploring seismicity and interior structure. Less attention is given to modeling Marsquake ground motion. This ground motion information is crucial to designing infrastructure (buildings and towers) to support Martian habitation, also envisioned in NASA’s Moon to Mars program. We take the challenge of estimating ground motion by analyzing single-station seismic recordings and integrating this information with recent findings. Given that ground motion is particularly relevant for major events (Mw>4.0 & occurred at shallow depths), our initial objective is to estimate the site effects of the largest recorded Marsquake (Mw4.7) based on HVSR (Horizontal over vertical spectral ratio) and PSA (pseudo-spectral acceleration). We are also estimating the PGA (peak ground acceleration) field in and around the epicenter of this event. This information is invaluable for engineers in selecting appropriate materials, designing structures, and modeling the mechanics between structure and materials.

Although HVSR applies to ambient noise recording of the diffuse wave field, we have estimated HVSR for the first arrival and coda wave recording separately. In both cases, the fundamental frequency is around 11Hz. The dominant ground motion corresponds to a 90-140° azimuth range. We have implemented a frequency-domain window rejection algorithm to estimate this HVSR. Moreover, we have additionally performed a statistical approach to evaluate the azimuthal variability of this seismic recording of interest. We are implementing the Southern California Earthquake Center (SCEC) Broadband Platform (BBP) to generate more practical ground motion information. We expect to produce synthetic and observed PSA and RotD50 (rotational ground motion considering 50% damping) from our ongoing efforts.

Since the Marsquake event of interest occurred at a 37° distance, we have performed a scenario-based seismic hazard assessment using the Openquake Toolkit of GEM. We have selected the Martian analog ground motion prediction equations developed for Eastern North America to estimate the PGA field close to the source, considering low seismicity and similar seismo-tectonic context. Although further careful selection of GMPE is still pending, our preliminary findings estimate the average PGA of 0.20g.