Pre‐Pliocene Extension around the Gulf of California and the transfer of Baja California to the Pacific Plate

Stock, J. M.; Hodges, Kip

doi:10.1029/tc008i001p00099

Cited by 383 publications

(341 citation statements)

References 53 publications

(17 reference statements)

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“…The formation of the GoC extensional province occurred in two phases: in the first stage the extension and continental separation formed continental marine basins, whereas during the second phase, a period of seafloor expansion and creation of transform faults took place, and these latter processes continue today (Stock and Hodges, 1989;Oskin et al, 2001;Bennett et al, 2007). As a consequence, the crustal structure at the margins of GoC is different with respect to the crustal structure along the plate boundary within the GoC (Fletcher and Munguía, 2000).…”

Section: Resultsmentioning

confidence: 99%

“…The evolution of the GoC is related to different tectonic processes, which began with the subduction of the Farallón plate and followed by continental and oceanic rift processes (Stock and Hodges, 1989;Atwater and Stock, 1998;Axen et al, 2000). Subsequently, the GoC was generated by the tectonic interaction of the Farallón, North America, and Pacific plates (Atwater, 1989;Martin-Barajas, 2000).…”

Section: Introductionmentioning

confidence: 99%

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An Attenuation Study of Body Waves in the South-Central Region of the Gulf of California, Mexico

Vidales-Basurto¹,

Castro²,

Huerta³

et al. 2014

Bulletin of the Seismological Society of America

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We studied the seismic attenuation of body waves in the south-central region of the Gulf of California (GoC) with records from the Network of Autonomously Recording Seismographs of Baja California (NARS-Baja), from the Centro de Investigación Científica y de Educación Superior de Ensenada's Broadband Seismological Network of the GoC (RESBAN), and from the ocean-bottom seismographs (OBS) deployed as part of the Sea of Cortez Ocean Bottom Array experiment (SCOOBA). We examine 27 well-located earthquakes reported in Sumy et al. (2013) that occurred from October 2005 to October 2006 with magnitudes (M w ) between 3.5 and 4.8. We estimated S-wave site effects by calculating horizontal-to-vertical spectral ratios and determined attenuation functions with a nonparametric model by inverting the observed spectral amplitudes of 21 frequencies between 0.13 and 12.59 Hz for the SCOOBA (OBS) stations and 19 frequencies between 0.16 and 7.94 Hz for NARS-Baja and RESBAN stations. We calculated the geometrical spreading and the attenuation (1=Q) factors for two distance intervals (10-120 and 120-220 km, respectively) for each frequency considered. The estimates of Q obtained with the SCOOBA (OBS) records for the interval 10-120 km indicate that the P waves attenuate more than S waves (Q P 34 1:2f 0:820:10 , Q S 59 1:1f 0:900:03 ) for frequencies between 0.6 and 12.6 Hz; whereas for the 120-220 km interval, where ray paths travel deeper, S waves attenuate more than P waves (Q P 117 1:3f 0:440:19 , Q S 51 1:2f 1:120:11 ). The estimates of Q obtained using NARS-Baja and RESBAN records, within 10-120 km, indicate that P waves attenuate more than S waves (Q P 69 1:2f 0:870:16 , Q S 176 1:4f 0:610:26 ) at frequencies between 0.3 and 6.3 Hz; whereas at the 120-220 km distance interval S waves attenuate slightly more than P waves (Q P 39 1:1f 0:640:06 , Q S 48 1:1f 0:370:07 ) at high frequencies (f > 3 Hz). These results, based on a unique OBS dataset, provide an indirect mean to constrain future models of the thermal structure beneath the GoC.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An Attenuation Study of Body Waves in the South-Central Region of the Gulf of California, Mexico

Vidales-Basurto¹,

Castro²,

Huerta³

et al. 2014

Bulletin of the Seismological Society of America

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“…[6] Subduction along northwestern Mexico ended from 17 to 12 Ma in a series of ridge jumps and microplate captures [Lonsdale, 1991;Stock and Hodges, 1989] that brought the Pacific and North American plates into contact along a transtensional margin. Although Pacific -North American plate motion was localized in the Gulf of California by 6 Ma [Oskin and Stock, 2003] and seafloor spreading in the gulf accommodated >85% of plate motion by 3.5 Ma [DeMets, 1995], how plate motion was accommodated during the ''proto-Gulf'' period (12 -6 Ma) is not well known and remains controversial [e.g., Stock and Hodges, 1989;Gans, 1997;Henry and Aranda-Gomez, 2000;Gans et al, 2003].…”

Section: Tectonic Overview Of Nw Mexicomentioning

confidence: 99%

“…Although vast regions of northern Mexico are believed to have experienced significant crustal extension during the Tertiary [Henry and Aranda-Gomez, 1992], the timing, magnitude, kinematics, spatial patterns and style of extension in this region remain poorly known. As a result, the driving forces of this extension and its relationship to the plate boundary change from subduction to transtension during the Miocene remain uncertain [Stock and Hodges, 1989;Gans, 1997;Henry and Aranda-Gomez, 2000].…”

Section: Introductionmentioning

confidence: 99%

Geologic, structural, and thermochronologic constraints on the tectonic evolution of the Sierra Mazatán core complex, Sonora, Mexico: New insights into metamorphic core complex formation

Wong

Gans

2008

Tectonics

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The Sierra Mazatán in northwestern Mexico is the southernmost metamorphic core complex in the North American Cordillera. Large‐magnitude Tertiary extension at Sierra Mazatán involved both ductile and brittle slip along a major normal fault that presently dips 10°–15° west. Extension was polyphase and involved an early period of extension from 25 to 23 Ma followed by major slip from 21 to 16 Ma. Total slip was ≤20 km and occurred at rates of 3–4 mm/a. This extension predated the plate boundary change to transtension at ∼12 Ma and was largely decoupled from relative Pacific–North American plate motion. Numerous lines of evidence suggest that the presently low‐angle normal fault initiated at a steep dip (50°–60°) and was rotated to lower angles during slip. When corrected for this tilting, fault corrugations at Sierra Mazatán had a similar geometry to the segmentation of many active normal faults, which is compatible with their origin as primary fault features. Many aspects of the Sierra Mazatán are comparable to large active normal faults, indicating that this core complex formed owing to prolonged extension on an otherwise typical high‐angle normal fault. Therefore, core complexes need not represent a fundamentally unique mode of crustal extension.

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“…The formation of the left step 'big bend' in the San Andreas fault occurred 12-4 Myr ago (Crowell 1968;Atwater 1970;Stock & Hodges 1989;Wright 1991) and is the most likely source of oblique convergence in southern California (Crowell 1968). Pacific plate motion relative to North America is now oriented in a NW direction, approximately parallel to the San Andreas fault in central California.…”

Section: Introductionmentioning

confidence: 99%

Anisotropy from SKS splitting across the Pacific-North America plate boundary offshore southern California

Ramsay¹,

Kohler²,

Davis³

et al. 2016

Geophys. J. Int.

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S U M M A R YSKS arrivals from ocean bottom seismometer (OBS) data from an offshore southern California deployment are analysed for shear wave splitting. The project involved 34 OBSs deployed for 12 months in a region extending up to 500 km west of the coastline into the oceanic Pacific plate. The measurement process consisted of removing the effects of anisotropy using a range of values for splitting fast directions and delay times to minimize energy along the transverse seismometer axis. Computed splitting parameters are unexpectedly similar to onland parameters, exhibiting WSW-ENE fast polarization directions and delays between 0.8 and 1.8 s, even for oceanic plate sites. This is the first SKS splitting study to extend across the entire boundary between the North America and Pacific plates, into the oceanic part of the Pacific plate. The splitting results show that the fast direction of anisotropy on the Pacific plate does not align with absolute plate motion (APM), and they extend the trend of anisotropy in southern California an additional 500 km west, well onto the oceanic Pacific plate. We model the finite strain and anisotropy within the asthenosphere associated with density-buoyancy driven mantle flow and the effects of APM. In the absence of plate motion effects, such buoyancy driven mantle flow would be NE-directed beneath the Pacific plate observations. The best-fit patterns of mantle flow are inferred from the tomography-based models that show primary influences from foundering higher-density zones associated with the history of subduction beneath North America. The new offshore SKS measurements, when combined with measurements onshore within the plate boundary zone, indicate that dramatic lateral variations in density-driven upper-mantle flow are required from offshore California into the plate boundary zone in California and western Basin and Range.

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Pre‐Pliocene Extension around the Gulf of California and the transfer of Baja California to the Pacific Plate

Cited by 383 publications

References 53 publications

An Attenuation Study of Body Waves in the South-Central Region of the Gulf of California, Mexico

An Attenuation Study of Body Waves in the South-Central Region of the Gulf of California, Mexico

Geologic, structural, and thermochronologic constraints on the tectonic evolution of the Sierra Mazatán core complex, Sonora, Mexico: New insights into metamorphic core complex formation

Anisotropy from SKS splitting across the Pacific-North America plate boundary offshore southern California

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