Monitoring performance using synthetic data for induced microseismicity by hydrofracking at the Wysin site (Poland)

Abstract

S U M M A R YIdeally, the performance of a dedicated seismic monitoring installation should be assessed prior to the observation of target seismicity. This work is focused on a hydrofracking experiment monitored at Wysin, NE Poland. A microseismic synthetic catalogue is generated to assess the monitoring performance during the pre-operational phase, where seismic information only concerns the noise conditions and the potential background seismicity. Full waveform, accounting for the expected spatial, magnitude and focal mechanism distributions and a realistic local crustal model, are combined with real noise recording to produce either event based or continuous synthetic waveforms. The network detection performance is assessed in terms of the magnitude of completeness (M c ) through two different techniques. First, we use an amplitude threshold, taking into the ratio among the maximal amplitude of synthetic waveforms and station-dependent noise levels, for different values of signal-to-noise ratio. The detection probability at each station is estimated for the whole data set and extrapolated to a broader range of magnitude and distances. We estimate an M c of about 0.55, when considering the distributed network, and can further decrease M c to 0.45 using arrays techniques. The second approach, taking advantage on an automatic, coherence-based detection algorithm, can lower M c to ∼ 0.1, at the cost of an increase of false detections. M c experiences significant changes during day hours, in consequence of strongly varying noise conditions. Moreover, due to the radiation patterns and network geometry, double-couple like sources are better detected than tensile cracks, which may be induced during fracking.

Characterization of Hydraulic Fractures Growth During the Äspö Hard Rock Laboratory Experiment (Sweden)

“…We proofed that waveform stacking and coherence analysis techniques allow detecting and locating automatically AEs, even using very high sampling rates. Our results extend the adoption of similar detection and location techniques, successfully applied for monitoring induced and natural seismic activity at local and regional distances (Matos et al, 2016;López-Comino et al, 2017a) also to very small-scale applications and for hydraulic fracturing, i.e. cm to dm scale fracturing events.…”

“…However, weak events could be lost when transient noises are generated in the fracturing area and poor trigger threshold are set with sequences characterized by short interevent times. Waveform stacking and coherence techniques have been tested for local seismic monitoring and induced seismicity improving the classical detection methods (Matos et al, 2016;López-Comino et al, 2017a). We consider continuous recordings and apply a recently developed automated full waveform detection and location algorithms (Lassie, https://gitext.gfzpotsdam.de/heimann/lassie, Heimann et al, 2017).…”

An Active Seismic Zone in Intraplate West Iberia Inferred From High‐Resolution Geophysical Data

“…In order to improve data coverage at the edges of the study area, we complemented the data set with data recorded by nearby permanent and temporary stations. We continuously scanned waveforms, searching for very low amplitude signals coherent across the network (López‐Comino, Cesca, Heimann et al, ; López‐Comino, Cesca, Kriegerowski et al, ; Matos et al, ). Preliminary locations were then computed using LOKI, a waveform‐based earthquake locator (Grigoli et al, , ).…”

Magnetic Anisotropy in Silurian Gas‐Bearing Shale Rocks From the Pomerania Region (Northern Poland)

“…In our opinion, such weak preferred orientation of magnetic minerals will have no influence on the propagation of induced fractures during hydraulic fracking. We suggest, rather, that the present stress regime is vitally important to the fracturing issue (e.g., Jarosiński, ; López‐Comino et al, ).…”