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Full-waveform event location and moment tensor inversion for induced seismicity

Chris Willacy, Ewoud van Dedem, Sara Minisini, Junlun Li, Jan-Willem Blokland, Indrajit Das and Alexander Droujinine
Full-waveform event location and moment tensor inversion for induced seismicity
Geophysics (March 2019) 84 (2): KS39-KS57

Abstract

Locating microearthquake events below complex heterogeneous overburden requires robust location methodologies that can honor multipathing in the seismic wavefield. We have developed two full-waveform event location methods that form a complementary solution for locating earthquakes and simultaneously deriving focal mechanisms via moment tensor inversion. The methods are based on the application of 3D elastic wavefield modeling, which is used to generate waveforms and extract wavefield attributes, for comparison to the observed field data. Events are located and focal mechanisms are derived via a multiparameter inversion, which minimizes the differences between synthetic and observed data. The results have been applied to the induced seismicity observed within the giant Groningen gas field, onshore Netherlands, where recorded earthquakes are triggered by stress changes, induced in the reservoir through pressure depletion. Locating events below the field is compounded by the presence of strong guided waves, which are trapped in the lower velocity reservoir interval. This complex multivalued wavefield is problematic for traditional event location methods, which assume a single traveltime arrival. We overcome this limitation by using all event arrivals in a wave-based solution to improve the accuracy of locating earthquakes and overcome the ambiguity of solving for location and the focal mechanism simultaneously. The event location methods have been applied to shallow and deep monitoring networks, and 150 events have been located with high accuracy. The interpretation of the earthquake activity indicates that the events studied originate from the movement of larger graben bounding faults, which are oriented in a north-northwest-south-southeast direction.


ISSN: 0016-8033
EISSN: 1942-2156
Coden: GPYSA7
Serial Title: Geophysics
Serial Volume: 84
Serial Issue: 2
Title: Full-waveform event location and moment tensor inversion for induced seismicity
Affiliation: Shell Global Solutions International, Amsterdam, Netherlands
Pages: KS39-KS57
Published: 201903
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 37
Accession Number: 2019-048354
Categories: SeismologyApplied geophysicsEconomic geology, geology of energy sources
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sect., sketch maps
N51°00'00" - N53°30'00", E03°15'00" - E07°15'00"
Secondary Affiliation: University of Science and Technology of China, CHN, ChinaShell International Exploration and Production, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 201925
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