Aftershocks of the 8 July, 1975 Canal de las Ballenas, Gulf of California, Earthquake

Munguía, Luis; Reichle, Michael; Reyes, Alfonso; Simons, Richard S.; Brune, James N.

doi:10.1029/gl004i011p00507

Cited by 20 publications

(9 citation statements)

References 10 publications

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“…Our coseismic fault models have a rupture depth of 13 km, equivalent within uncertainties to the seismic estimates of 10-15 km for the base of earthquake nucleation along transforms in the Gulf of California [Munguia et al, 1977;Goff et al, 1987;Castro et al, 2010Castro et al, , 2011Sumy et al, 2013] but deeper than our estimates for the interseismic fault locking depth. Agreement between both parameters is not expected, Journal of Geophysical Research: Solid Earth 10.1002/2015JB011959 because the two approaches estimate the depth of the brittle-ductile transition zone over different time scales.…”

Section: Coseismicsupporting

confidence: 73%

“…About~90% of the full North America-Pacific plate relative motion rate (approximately 43-47 mm/yr) is accommodated along the Gulf of California [DeMets et al, 1990[DeMets et al, , 1994DeMets and Dixon, 1999;Dixon et al, 2000a;Plattner et al, 2007Plattner et al, , 2009. Because of the submarine setting, however, crustal deformation studies have largely been limited to the interpretation of faulting processes that occur over short time scales in the seismogenic zone [Munguia et al, 1977;Goff et al, 1987;Rebollar et al, 2001;Rodriguez-Lozoya et al, 2008;Castro et al, 2010Castro et al, , 2011Sumy et al, 2013;Lopez-Pineda et al, 2014].…”

Section: Introductionmentioning

confidence: 99%

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Space geodetic observation of the deformation cycle across the Ballenas Transform, Gulf of California

et al. 2015

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The Gulf of California, Mexico, accommodates ~90% of North America‐Pacific plate relative motion. While most of this motion occurs on marine transform faults and spreading centers, several fault segments in the central Gulf come close to peninsular Baja California. Here we present Global Positioning System and interferometric synthetic aperture radar data near the Ballenas transform fault, separating the peninsula from Angel de la Guarda Island. We observe interseismic motion between June 2004 and May 2009 and displacements associated with the 3 August 2009 Mw 6.9 earthquake. From the interseismic data we estimate a locking depth of 9–12.5 km and a slip rate of 44.9–48.1 mm/yr, indicating that faults east of Angel de la Guarda deform at negligible rates and that the Ballenas Transform accommodates virtually all of the relative motion between the North American plate and the Baja California microplate. Our preferred model for coseismic slip on a finite rectangular fault plane suggests 1.3 m of strike‐slip displacement along a vertical rupture plane that is 60 km long and extends from the surface to a depth of 13 km in the eastern Ballenas Channel, striking parallel to Baja California‐North America relative plate motion. These estimates agree with the seismic moment tensor and the location of the major foreshock and aftershocks and are compatible with the fault location identified from high‐resolution bathymetric mapping. The geodetic moment is 33% higher than the seismic moment in part because some afterslip and viscous flow in the first month after the earthquake are included in the geodetic estimate. Coulomb stress changes for adjacent faults in the Gulf are consistent with the location of smaller aftershocks following the 2009 main shock and suggest potential triggering of the 12 April 2012 Mw 6.9 Guaymas earthquake.

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Section: Coseismicsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Space geodetic observation of the deformation cycle across the Ballenas Transform, Gulf of California

et al. 2015

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“…However, the assumed fault width of 12 km is also based on the hypocentral distribution of the previous 1975 earthquake sequence. Munguía et al (1977) found that the aftershocks of the 1975 Canal de Ballenas earthquakes were located up to 10-15 km deep. The rupture area thus Figure 8.…”

Section: Resultsmentioning

confidence: 99%

“…2). For instance, on 8 July 1975 an event with M s 6.5 occurred west of the island Angel de la Guarda (Munguía et al, 1977). Moderate magnitude earthquakes have also occurred in this region to the north, in the lower Delfin basin, on 26 November 1997 (M 5.5) and south of Angel de la Guarda island on 12 November 2003 (M w 5.4) and 24 September 2004 (M w 5.8).…”

Section: Introductionmentioning

confidence: 97%

“…The Global Centroid Moment Tensor (CMT) catalog lists 17 earthquakes with moment magnitudes 5:2 ≤ M w ≤ 6:9 in this region between 1976 and 2009. We plotted these events in Figure 2, together with the focal mechanism determined by Munguía et al (1977) for the July 1975 (M s 6.5) earthquake. The focal mechanisms of most of these events are strike-slip, as expected for transform faulting along the Pacific-North American plate boundary.…”

Section: Introductionmentioning

confidence: 99%

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The 3 August 2009 Mw 6.9 Canal de Ballenas Region, Gulf of California, Earthquake and Its Aftershocks

Castro

Valdés‐González

Shearer

et al. 2011

Bulletin of the Seismological Society of America

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On 3 August 2009 an earthquake of magnitude M w 6.9 occurred near Canal de Ballenas, in the north-central region of the Gulf of California, Mexico. The focal mechanism of the main event, reported in the Global Centroid Moment Tensor (CMT) catalog, is right lateral strike-slip with a strike of 216°and a dip of 78°. The initial location reported by the National Seismological Service of Mexico [Servicio Sismólogico Nacional (SSN)] and the Array Network Facility (ANF) suggested that the epicenter was on the North American plate near the Tiburón fault, which is considered inactive. This earthquake was preceded by a magnitude m b 5.5 event that occurred about 5 min before. In the next 40 min after the main event two aftershocks with magnitudes m b 4.9 and M w 6.2 occurred, and on 5 August a third aftershock of M w 5.7 was located in the Canal de Ballenas region. The events of August 2009 were recorded by the regional stations of the broadband network Red Sismólogica de Banda Ancha (RESBAN) that Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE) operates and by stations of the SSN also located in the region of the Gulf of California. We used body-wave arrivals to determine precise epicentral locations and to estimate the rupture area of this important sequence of earthquakes. The resulting hypocentral coordinates indicate that the main event of this sequence occurred along the Canal de Ballenas transform fault, with a rupture length of 50 km. Based on the aftershock distribution, we estimate that the main event had a rupture area of approximately 600 km 2 , an average slip of 1.3 m, and a stress drop of 2.2 MPa.

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The 2006 Bahía Asunción Earthquake Swarm: Seismic Evidence of Active Deformation Along the Western Margin of Baja California Sur, Mexico

Munguía¹,

Mayer²,

Aguirre³

et al. 2015

Pageoph Topical Volumes

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Aftershocks of the 8 July, 1975 Canal de las Ballenas, Gulf of California, Earthquake

Cited by 20 publications

References 10 publications

Space geodetic observation of the deformation cycle across the Ballenas Transform, Gulf of California

Space geodetic observation of the deformation cycle across the Ballenas Transform, Gulf of California

The 3 August 2009 Mw 6.9 Canal de Ballenas Region, Gulf of California, Earthquake and Its Aftershocks

The 2006 Bahía Asunción Earthquake Swarm: Seismic Evidence of Active Deformation Along the Western Margin of Baja California Sur, Mexico

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