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Stress Field Variations and Earthquake Source Mechanisms Associated with Wastewater Induced Seismicity in Southern Kansas, USA

Session: Mechanisms of Induced Seismicity: Pressure Diffusion, Elastic Stressing and Aseismic Slip II

Type: Oral

Date: 4/19/2021

Presentation Time: 05:15 PM Pacific

Description: 

During the last 10 years, a strong increase of seismicity rates was observed in the conterminous USA and linked to the injection of huge amounts of wastewater from oil and gas production in unconventional hydrocarbon reservoirs. Here, we calculated 549 moment tensors of induced earthquakes with a moment magnitude M_W ≤ 4.9 in southern Kansas to study their source mechanisms and their relation to injection activity. We observed that approximately 17% of the analyzed events had significant non-double-couple components, and these events mostly occurred near the two largest local earthquakes (the M_W 4.9 Milan and M_W 4.3 Harper earthquakes). Then, we inverted for the stress field orientation and determined that most of the region lies within a transtensional stress regime, with a maximum horizontal stress σ_Hmax trending N75°E. Furthermore, in the epicentral area of the M_W 4.9 Milan earthquake, the σ_Hmax trend is rotated to about S80°E. Locally, we also highlighted two areas that display a change in the stress field orientation with depth, from transtensional above 5.5 km depth to strike-slip deeper in the basement. Finally by relating the resolved fault geometries to the obtained local stress field orientation, we find that most of the activated fault planes were optimally oriented to the current stress field and thus small stress perturbations caused by the water injection could lead to failure.

Presenting Author: Amandine Amemoutou

Student Presenter: Yes

Authors