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Title: Local beamforming and back-projection of induced earthquakes in Helsinki, southern Finland
Seismic array processing is routinely used to infer detailed earthquakeproperties of intermediate and large events, however, the sourceproperties of microseismicity often remain elusive. In this study, weuse high signal-to-noise ratio seismograms of 204 earthquakes induced bythe 6 km deep 2018 Espoo/Helsinki geothermal stimulation to evaluate thecapabilities of beamforming and back-projection array methods. We showthat mini array beamforming is sensitive to medium heterogeneity andrequires calibration to mitigate systematic slowness biases.A combinedand wave back-projection approach significantly improves depthresolution, reducing offsets to catalogue locations from km to m.Supported by numerical experiments, we demonstrate that back-projectionswimming patterns can constrain focal mechanisms. Our results imply thatback-projection of data collected over a wide azimuthal range can beused to monitor and characterize local-scale microseismicity, whereasbeamforming calibration requires independently obtained referenceobservations.  more » « less
Award ID(s):
2311206
PAR ID:
10536424
Author(s) / Creator(s):
; ;
Publisher / Repository:
Authorea, Inc.
Date Published:
Format(s):
Medium: X
Institution:
Authorea, Inc.
Sponsoring Org:
National Science Foundation
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