P‐wave image of the Peninsular Ranges Batholith, southern California

Magistrale, Harold; Sanders, Christopher O.

doi:10.1029/95gl02241

Cited by 37 publications

(38 citation statements)

References 14 publications

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“…This is the side that has more damaged rock in our geological studies and in the seismic imaging of LEWIS et al (2005). These results are in agreement with regional imaging of MAGISTRALE and SANDERS (1995) and SHAPIRO et al (2005), who show the same sense of velocity contrast in the Anza area and farther to the southeast. The existence of more rock damage on the side of the fault that has faster seismic velocity at seismogenic depth is expected if a material interface controls the preferred propagation direction on the fault.…”

Section: Asymmetry Of Structural Properties In Light Of Velocity Strusupporting

confidence: 80%

Geological Observations of Damage Asymmetry in the Structure of the San Jacinto, San Andreas and Punchbowl Faults in Southern California: A Possible Indicator for Preferred Rupture Propagation Direction

Dor

Rockwell

Ben‐Zion

2006

Pure appl. geophys.

184

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We present new in situ observations of systematic asymmetry in the pattern of damage expressed by fault zone rocks along sections of the San Andreas, San Jacinto, and Punchbowl faults in southern California. The observed structural asymmetry has consistent manifestations at a fault core scale of millimeters to meters, a fault zone scale of meters to tens of meters and related geomorphologic features. The observed asymmetric signals are in agreement with other geological and geophysical observations of structural asymmetry in a damage zone scale of tens to hundreds of meters. In all of those scales, more damage is found on the side of the fault with faster seismic velocities at seismogenic depths. The observed correlation between the damage asymmetry and local seismic velocity structure is compatible with theoretical predictions associated with preferred propagation direction of earthquake ruptures along faults that separate different crustal blocks. The data are consistent with a preferred northwestward propagation direction for ruptures on all three faults. If our results are supported by additional observations, asymmetry of structural properties determined in field studies can be utilized to infer preferred propagation direction of large earthquake ruptures along a given fault section. The property of a preferred rupture direction can explain anomalous behavior of historic rupture events, and may have profound implications for many aspects of earthquake physics on large faults.

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Section: Asymmetry Of Structural Properties In Light Of Velocity Strusupporting

confidence: 80%

Geological Observations of Damage Asymmetry in the Structure of the San Jacinto, San Andreas and Punchbowl Faults in Southern California: A Possible Indicator for Preferred Rupture Propagation Direction

Dor

Rockwell

Ben‐Zion

2006

Pure appl. geophys.

184

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“…This compositional boundary, as suggested by Thomson and Girty (1994) and Schmidt (2000), has provided a mechanical weakness in the crust along which the Mesozoic intra-arc strain was concentrated. Also, Magistrale and Sanders (1995) proposed that Quaternary fault development also has been localized at this discontinuity.…”

Section: Peninsular Ranges Batholithmentioning

confidence: 97%

Geochronological constraints on the tectonic history of the Peninsular Ranges Batholith of Alta and Baja California: Tectonic implications for western México

Ortega‐Rivera¹

2003

Tectonic Evolution of Northwestern Mexico and the Southwestern USA

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A compilation of existing age data and new age determinations (U/Pb zircon, 40 Ar/ 39 Ar step-heating, K/Ar, Rb/Sr, and apatite fi ssion-track dates) for the Peninsular Ranges batholith of Alta and Baja California provides geochronological constraints on the tectonic history of the Peninsular Ranges batholith and tectonic implications for western México.The plutons of the Peninsular Ranges batholith of Alta and Baja California between the 28°N and 34°N parallels were emplaced from west to east between ca. 140 to 80 Ma (U/Pb zircon dates) and display 40 Ar/ 39 Ar hornblende and biotite plateau dates that range from 118 to 83 Ma and 116 to 80 Ma, respectively, and biotite K/Ar dates as young as 65 Ma. Rapid cooling is indicated by the small differences in U/Pb zircon and cogenetic 40 Ar/ 39 Ar dates. Mineral pairs having mainly concordant dates yield 40 Ar/ 39 Ar cooling ages that also systematically decrease from southwest to northeast. Also, monotonic eastward younging of ages across various plutons was found as was previously reported for the Sierra San Pedro Mártir pluton. This systematic regional and local eastward younging may be explained by the systematic tilting of pluton-sized crustal blocks containing individual plutons.The northeastward decrease in ages across the Peninsular Ranges batholith and across some of its plutons is therefore attributed to regional eastward migration of granitic intrusion foci combined with rapid differential exhumation histories and superimposed east-side-up tilting of crustal-sized blocks containing some of the plutons and beautifully exemplifi es the short time lapse between batholith intrusion and unroofi ng.Additionally, apatite fi ssion-track dates from samples collected across the Peninsular Ranges, from Ensenada to San Felipe, Baja California, establish that there is also an eastward younging of ages from 104 Ma to 51 Ma from west to east and also across plutons. The fi ssion-track dates indicate that from west to east, present exposures of much of the western Peninsular Ranges batholith have been within «3 km of the Earth's surface (assuming a normal geothermal gradient) since Early Cretaceous time, and that by early Tertiary time, much of the eastern Peninsular Ranges had cooled to temperatures of <110 °C, indicating rapid exhumation histories and superimposed east-side-up tilting shown by younger ages at higher elevations within plutons. The batholith was suffi ciently uplifted during the Late Cretaceous such that 10-15 km of material was eroded off the eastern part of the batholith by early Paleocene time.Furthermore, a regional compilation of the available age data for western México provides geochronological constraints for the testing of controversial paleomagnetic and geological models for the tectonic evolution of the Mesozoic Peninsular Ranges of

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“…For example, mafi c compositions tend to be more resistant to both brittle and ductile deformation than felsic rock types (Jaeger and Cook, 1979;Rutter and Brodie, 1992). Magistrale and Sanders (1995) suggested that the San Jacinto fault zone developed along part of a compositional boundary or discontinuity within the Peninsular Ranges batholith (Fig. 2).…”

Section: Introductionmentioning

confidence: 99%

Geophysical and isotopic mapping of preexisting crustal structures that influenced the location and development of the San Jacinto fault zone, southern California

Langenheim

Jachens

Morton

et al. 2004

Geol Soc America Bull

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We examine the role of preexisting crustal structure within the Peninsular Ranges batholith on determining the location of the San Jacinto fault zone by analysis of geophysical anomalies and initial strontium ratio data. A 1000-km-long boundary within the Peninsular Ranges batholith, separating relatively mafi c, dense, and magnetic rocks of the western Peninsular Ranges batholith from the more felsic, less dense, and weakly magnetic rocks of the eastern Peninsular Ranges batholith, strikes north-northwest toward the San Jacinto fault zone. Modeling of the gravity and magnetic fi eld anomalies caused by this boundary indicates that it extends to depths of at least 20 km. The anomalies do not cross the San Jacinto fault zone, but instead trend northwesterly and coincide with the fault zone. A 75-km-long gradient in initial strontium ratios (Sr i ) in the eastern Peninsular Ranges batholith coincides with the San Jacinto fault zone. Here rocks east of the fault are characterized by Sr i greater than 0.706, indicating a source of largely continental crust, sedimentary materials, or different lithosphere. We argue that the physical property contrast produced by the Peninsular Ranges batholith boundary provided a mechanically favorable path for the San Jacinto fault zone, bypassing the San Gorgonio structural knot as slip was transferred from the San Andreas fault 1.0-1.5 Ma. Two historical M6.7 earthquakes may have nucleated along the Peninsular Ranges batholith discontinuity in San Jacinto Valley, suggesting that Peninsular Ranges batholith crustal structure may continue to affect how strain is accommodated along the San Jacinto fault zone.

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P‐wave image of the Peninsular Ranges Batholith, southern California

Cited by 37 publications

References 14 publications

Geological Observations of Damage Asymmetry in the Structure of the San Jacinto, San Andreas and Punchbowl Faults in Southern California: A Possible Indicator for Preferred Rupture Propagation Direction

Geological Observations of Damage Asymmetry in the Structure of the San Jacinto, San Andreas and Punchbowl Faults in Southern California: A Possible Indicator for Preferred Rupture Propagation Direction

Geochronological constraints on the tectonic history of the Peninsular Ranges Batholith of Alta and Baja California: Tectonic implications for western México

Geophysical and isotopic mapping of preexisting crustal structures that influenced the location and development of the San Jacinto fault zone, southern California

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