News Archive for December 2021

$Study area and hybrid-frequency waveform earthquakes (EHWs): (a) hydraulic fracturing activity and seismicity in northeast British Columbia, Canada; the top-right inset shows the geographic location of the study area (red rectangle); blue diamonds: hydraulic fracturing injection wells between January 1, 2014 and December 31, 2016, reported by the British Columbia Oil and Gas Commission; yellow dots: earthquakes during the same period; stars: 10 M 4-5 earthquakes since 2008; black rectangle: study area in which EHWs occurred; (b, c) comparison between representative examples of a typical induced event (black trace) and an EHW (purple trace); both waveforms are from the vertical component of station MG03 with comparable source-station distance (1.32 km vs. 1.65 km) and magnitudes (MW1.5); manually picked P/S-arrivals are marked; the comparison of P/S-pulse shape demonstrates the relatively wider pulses for EHWs; (d, e) the same as (b) and (c) but for waveforms recorded at station MG02; both events show longer coda durations with slightly larger epicentral distances; note that although both types of events have extended coda durations, the EHW contains a relatively larger proportion of lower-frequency energy in the coda. Image credit: Yu et al., doi: 10.1038/s41467-021-26961-x.$