51ÁÔÆæÈë¿Ú

Abstract:

We report confirmed impact sources for two seismic events on Mars detected by the NASA InSight mission. These events have been positively associated with fresh impact craters identified from orbital images, which match predicted locations and sizes to within a factor of 3, and have formation time constraints consistent with the seismic event dates. They are both of the very high frequency family of seismic events and are present with chirps (dispersed infrasound/acoustic waves). This brings the total number of confirmed Martian impact-related seismic events to eight thus far. All seismic events with chirp signals have now been confirmed as having been caused by impact cratering events. This includes all seismic activity within 100 km of the lander and two out of the four events with source locations between 100 and 300 km distance.ISSN:2632-333

Abstract:

Template matching has become a cornerstone technique of observational seismology. By taking known events, and scanning them against a continuous record, new events smaller than the signal-to-noise ratio can be found, substantially improving the magnitude of completeness of earthquake catalogues. Template matching is normally used in an array setting, however as we move into the era of planetary seismology, we are likely to apply template matching for very small arrays or even single stations. Given the high impact of planetary seismology studies on our understanding of the structure and dynamics of non-Earth bodies, it is important to assess the reliability of template matching in the small-n setting. Towards this goal, we estimate a lower bound on the rate of false positives for single-station template matching by examining the behaviour of correlations of totally uncorrelated white noise. We find that, for typical processing regimes and match thresholds, false positives are likely quite common. We must therefore be exceptionally careful when considering the output of template matching in the small-n setting.

Abstract:

Admission to doctoral study is a crucial step in the academic pipeline, but discriminatory procedures can disproportionately impact students from ethnic minority backgrounds. We show how these policies contribute to inequity in the geosciences and propose strategies for change.