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Near-fault monitoring reveals combined seismic and slow activation of a fault branch within the Istanbul-Marmara seismic gap in northwest Turkey

Patricia Martinez-Garzon, Virginie Durand, Stephan Bentz, Grzegorz Kwiatek, Georg Dresen, Taylan Turkmen, Murat Nurlu and Marco Bohnhoff
Near-fault monitoring reveals combined seismic and slow activation of a fault branch within the Istanbul-Marmara seismic gap in northwest Turkey
Seismological Research Letters (August 2021) 92 (6): 3743-3756

Abstract

Various geophysical observations show that seismic and aseismic slip on a fault may occur concurrently. We analyze microseismicity recordings from a temporary near-fault seismic network and borehole strainmeter data from the eastern Marmara region in northwest Turkey to track seismic and aseismic deformation around the hypocentral region of an M (sub w) 4.5 earthquake in 2018. A slow transient is observed that lasted about 30 days starting at the time of the M (sub w) 4.5 event. We study about 1200 microseismic events that occurred during 417 days after the M (sub w) 4.5 event around the mainshock fault rupture. The seismicity reveals a strong temporal clustering, including four episodic seismic sequences, each containing more than 30 events per day. Seismicity from the first two sequences displayed typical characteristics driven by aseismic slip and/or fluids, such as the activation of a broader region around the mainshock and swarm-like topology. The third and fourth sequences correspond to typical mainshock-aftershock sequences. These observations suggest that slow slip and potentially fluid diffusion along the fault plane could have controlled the seismicity during the initial 150 days following the M (sub w) 4.5 event. In contrast, stress redistribution and breaking of remaining asperities may have caused the activity after the initial 150 days. Our observation from a newly installed combined dense seismic and borehole strainmeter network follows an earlier observation of a slow transient occurring in conjunction with enhanced local seismic moment release in the same region. This suggests a frequent interaction of seismic and aseismic slip in the Istanbul-Marmara seismic gap.


ISSN: 0895-0695
EISSN: 1938-2057
Serial Title: Seismological Research Letters
Serial Volume: 92
Serial Issue: 6
Title: Near-fault monitoring reveals combined seismic and slow activation of a fault branch within the Istanbul-Marmara seismic gap in northwest Turkey
Affiliation: Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Potsdam, Germany
Pages: 3743-3756
Published: 20210811
Text Language: English
Publisher: Seismological Society of America, El Cerrito, CA, United States
References: 48
Accession Number: 2021-055759
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch maps
N40°30'00" - N41°00'00", E28°45'00" - E29°30'00"
Secondary Affiliation: Disaster and Emergency Management Authority Turkey (AFAD), TUR, Turkey
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 202139
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