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The January 2014 northern Cuba earthquake sequence; unusual location and unexpected source mechanism variability

Jochen Braunmiller, Glenn Thompson and Stephen R. McNutt
The January 2014 northern Cuba earthquake sequence; unusual location and unexpected source mechanism variability
Bulletin of the Seismological Society of America (June 2019) 109 (3): 919-928

Abstract

On 9 January 2014, a magnitude M (sub w) 5.1 earthquake occurred along the Bahamas-Cuba suture at the north coast of Cuba, revealing a surprising seismic hazard source for southern Florida where it was widely felt. Because of its location, the event and its aftershocks were recorded only at far distances, resulting in high-detection thresholds and low location accuracy. We use regional seismograms to determine source mechanisms and relative locations of the seven largest events in the sequence. Aftershock relocations relative to the mainshock, obtained by cross-correlating Rayleigh waves, indicate a tight event cluster. Aligning low-pass-filtered (T > 10 s) vertical seismograms from the closest site, station 061Z in southern Florida, on the P-wave arrival reveals a surprising flip of the surface-wave polarity for some aftershocks relative to the mainshock. Regional moment tensor inversion confirms that the mechanisms changed. Consistent with the Global Centroid Moment Tensor solution, we find an approximately east-west-trending normal-faulting mechanism for the main event and one aftershock. Three aftershocks indicate approximately east-west-trending reverse faulting with P and T axes flipped relative to the normal-faulting events. Within uncertainties, depths of all events are indistinguishable and indicate shallow faulting (< or =10 km). One intriguing possible interpretation is that both families ruptured the same fault with reverse mechanisms compensating for dynamic overshooting. However, activity could instead be slightly separated with reverse mechanisms below extension or with slip on conjugate faults. The shallow source depths along the suture indicate that larger and potentially tsunamigenic earthquakes could occur offshore of northern Cuba, presenting a possible hazard locally and to Florida and the Bahamas.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 109
Serial Issue: 3
Title: The January 2014 northern Cuba earthquake sequence; unusual location and unexpected source mechanism variability
Affiliation: University of South Florida, School of Geosciences, Tampa, FL, United States
Pages: 919-928
Published: 201906
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 33
Accession Number: 2019-062011
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, sketch maps
N22°00'00" - N26°00'00", W83°00'00" - W78°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201915
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