The Similarity Between Induced and Natural Earthquakes: A View From the Non-Double-Couple Component

Date: 4/26/2019

Time: 06:00 PM

Room: Fifth Avenue

Focal mechanisms of induced earthquakes reflect anthropogenic contributions to the pre-existing geological features and fault slippages. In this paper, we examine the fault-related (double-couple, DC) and possibly fluid-related (non-double-couple, non-DC) mechanisms of induced earthquakes at a regional scale (M2-6). We systematically compare the well-resolved focal mechanisms of 35 shallow events in the Western Canada Sedimentary Basin, among which 14 were induced by hydraulic fracturing and one by secondary recovery. Overall, M>4 natural and induced earthquakes show consistent fault plane solutions when located close to each other. Thus, their focal mechanisms are likely pre-determined by event locations, indicating origins that are dominated by tectonic stress release. Limited (but consistent) non-DC components are obtained from the hydraulic-fracturing induced seismicity in central Alberta. We interpret the persistent compensated-linear-vector-dipole (CLVD) components (M2.1-3.8) as reflecting 1) fracture growth during hydraulic-fracturing stimulation and/or 2) co-slipping of the dextral transentional faults. Both explanations are widely adopted to explain the CLVD components observed in volcanic regions. We further expand the moment tensor decomposition analysis to four representative classes of induced seismicity globally and find that the overall contribution of non-DC components is largely comparable between induced and tectonic earthquakes.

Presenting Author: Ruijia Wang

Authors