Many Swiss microearthquake sequences have been analyzed using relative location techniques, which often allowed constraining active fault planes and tectonic processes that drive seismicity. Yet, often the number of located earthquakes was too small to infer details of the space-time evolution of the sequences or their statistical properties, and thus resolve clear seismicity patterns and their driving mechanisms.We present a nearly automatic workflow that combines well-established seismological analysis techniques to improve the completeness of detected and located earthquakes of a sequence. Starting from a manual catalog (magnitude of completeness, Mc ≈ 1.0−1.5), we assemble a template set and perform a matched filter analysis on a single station with highest SNR. This allows us to detect events of local magnitude ML< 0.0. The waveform similarity is further exploited to derive detection magnitudes. The enhanced catalog is then statistically analyzed to derive high-resolution temporal evolutions of the Gutenberg−Richter a- and b-values, and consequently the occurrence probability of larger events. Strong events are located using relative double-difference, which usually improves the number of well-relocated events by a factor of 2−5.This workflow allows us to significantly enhance the analysis of spatiotemporal behavior of natural and induced microearthquake sequences, which we use to monitor commercial and scientific fluid injections in near real-time. We implemented this workflow in the open-source Python/PostgreSQL toolboxQuakeMatch.We discuss the capabilities of QuakeMatch with examples of induced microearthquake sequences associated with various geothermal projects monitored by the Swiss Seismological Service in the framework of the GEOBEST2020+ project.
The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)