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Summary of Proposal LAN2200

TitleTriggered seismicity due to quarry activity and mining
Investigator Lohman, Rowena - Cornell University, Earth and Atmospheric Sciences
Team Member
Associate van der Lee, Suzan - Northwestern University, Department of Earth and Planetary Sciences
Assistant Professor Lohman, Rowena - Cornell University, Earth and Atmospheric Sciences
SummaryHere we propose to examine data spanning a small earthquake that occurred in association with quarrying activity near the city of Chicago, Illinois. Our objective will be to constrain the location and potentially the mechanism of the November 4, 2013, shallow M3.2 earthquake, which occurred 7 seconds after a quarry blast in a western Chicago suburb. The dearth of seismic station in this region has precluded a determination as to whether the earthquakes epicenter was in or near the quarry. Estimates of the focal mechanism and location based on the existing seismic data suggest that the event occurred at a depth of less than a kilometer, but place only weak constraints on the map view location relative to the quarry, or on the style of associated faulting. The data requirements for this task can largely be fulfilled with existing archive data, with some provision for additional data in order to characterize the natural variability of the signal (phase and coherence) due to effects from vegetation, snow cover, etc., in this suburban region, as well as any continued deformation at the site. We also request a small allocation for study of future events, when they occur and are associated with existing pre-seismic imagery. We are focusing on one particular track of StripMap data which included an acquisition the preceding spring and now also includes data from several weeks after the earthquake. While coherence over this time period may not be optimal, the Co-I (Lohman) has had reasonable results with data spanning longer time intervals in the Pacific Northwest when sufficient human infrastructure (streets, rooftops) were present. The area in question includes numerous such features at a spatial density that should reasonably sample the deformation field of a M3.2 earthquake at 1 km depth up to a depth of around 100 m. Even a null results would be of interest, particularly if the decorrelated region was restricted to the quarry - we would then be able to make a case about the earthquake either being located within the quarry or at a depth below our noise threshold (which we would estimate directly from the InSAR data). Deliverables would include maps of the coherence for all available interferograms, estimates of the constraints on the earthquake hypocenter and errors on those estimates, or evaluation of the significance of any null results, through reports and publications. Modeling of any observed deformation will initially be performed using the best-fit dislocation in an elastic half space, with modification for more realistic sources and elastic structures if the data quality suggests that this is warranted. Funding comes from Co-I Lohmans startup funds and from existing grants held by Co-I van der Lee.

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