Gravity anomalies, Quaternary vents, and Quaternary faults in the southern Cascade Range, Oregon and California: Implications for arc and backarc evolution

Blakely, Richard J.; Christiansen, Robert L.; Guffanti, Marianne; Wells, Ray E.; Donnelly‐Nolan, Julie M.; Muffler, L. J. Patrick; Clynne, Michael A.; Smith, J. G.

doi:10.1029/97jb01516

Cited by 52 publications

(41 citation statements)

References 44 publications

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“…Mafi c igneous intrusions have been shown to infl uence seismicity and faulting in several regions, such as the Mississippi embayment of the central United States (Hildenbrand and Hendricks, 1995), the Death Valley region of California (Blakely et al, 1999), the Klamath Falls, Oregon, area (Blakely et al, 1997), the Mojave Desert (Langenheim and Jachens, 2001), and Mount Etna, Italy (Villasenor et al, 1998). The more mafi c western Peninsular Ranges batholith, extending to at least mid-crustal depths, would, by analogy, be stronger and more resistant to deformation than the felsic eastern Peninsular Ranges batholith.…”

Section: Infl Uence Of Prebatholithic Structure On the Development Ofmentioning

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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Section: Infl Uence Of Prebatholithic Structure On the Development Ofmentioning

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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“…1) (Wills, 1991;Muffl er et al, 1994;Blakely et al 1997;Walker, 2008). Normal faulting and recurring volcanic activity from more than 500 vents over the past 7 m.y.…”

Section: Introductionmentioning

confidence: 97%

“…2). This change in geometry likely refl ects the infl uence of regional tectonic patterns, particularly the Walker Lane belt to the southeast, which transferred dextral shear into the Lassen region (Blakely et al, 1997;Muffl er et al, 2008), creating the left-stepping segment patterns and potentially driving the ongoing activity of the later scarps (Walker, 2008).…”

Section: Introductionmentioning

confidence: 97%

Revised earthquake hazard of the Hat Creek fault, northern California: A case example of a normal fault dissecting variable-age basaltic lavas

Blakeslee

Kattenhorn

2013

Geosphere

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Normal faults in basalt have distinctive surface-trace morphologies and earthquake evidence that provide information about the slip behavior and earthquake potential. The 47-km-long Hat Creek fault in northern California (USA), a useful case example of this fault style, is a segmented fault system located along the western margin of the Modoc Plateau that is a regional earthquake hazard. In response to interaction with sporadically active volcanic systems, surface ruptures have progressively migrated westward since the late Pleistocene, with older scarps being successively abandoned. The most recent earthquake activity broke the surface through predominantly ca. 24 ka basaltic lavas, forming a scarp with a maximum throw of 56 m. Past work by others identifi ed 7-8 left-stepping scarp segments with a combined length of 23.5 km, but did not explicitly address the throw characteristics, fault evolution, slip history, or earthquake potential. We address these defi ciencies in our understanding of the fault system with new fi eld observations and mapping that suggest the active scarp contains 2 additional segments and is at least 6.5 km longer than previously mapped, thus increasing the knowledge of the regional seismic hazard. Our work details scarp geomorphic styles and slip-analysis techniques that can be applied to any normal-faulted basalt environment. Applied to the Hat Creek fault, we estimate that a surface-breaking rupture could produce an earthquake of ~M w (moment magnitude) 6.7 and a recurrence interval of 667 ± 167 yr in response to a rapid slip rate in the range 2.2-3.6 mm/yr, creating a moderate risk given a lack of historical earthquake events.

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“…Medicine Lake Volcano is located near the boundary of the extensional Basin and Range province and north-south trending normal faults are present in and around the volcano Dzurisin, 1991;Blakely et al, 1997;Clausen et al, 2006). As noted previously, there may be a component of dextral shear across the MLV area.…”

Section: Hypotheses For the Origin Of The Summit Basin Of MLVmentioning

confidence: 99%

“…The Likely Fault Zone southeast of MLV primarily accommodates dextral shear (Sawyer and Bryant, 1995). Blakely et al (1997) compared regional gravity anomalies, fault orientations, and vent density and location to infer that the northwest trending faults reflect the propagation of dextral shear strain from the Walker Lane belt into the Cascades arc in Oregon. Field measurements based largely on striated fractures in the MLV area indicate substantial components of primarily dextral strike slip shear (Nemčok, Energy and Geoscience Institute, unpublished data, 2006).…”

mentioning

confidence: 99%

Tectonic Versus Volcanic Origin of the Summit Depression at Medicine Lake Volcano, California

Gwynn¹

2010

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Medicine Lake Volcano is a Quaternary shield volcano located in a tectonically complex and active zone at the transition between the Basin and Range Province and the Cascade Range of the Pacific Province. The volcano is topped by a 7x12 km elliptical depression surrounded by a discontinuous constructional ring of basaltic to rhyolitic lava flows. This thesis explores the possibility that the depression may have formed due to regional extension (rift basin) or dextral shear (pull-apart basin) rather than through caldera collapse and examines the relationship between regional tectonics and localized volcanism. Existing data consisting of temperature and magnetotelluric surveys, alteration mineral studies, and core logging were compiled and supplemented with additional core logging, field observations, and fault striae studies in paleomagnetically oriented core samples. These results were then synthesized with regional fault data from existing maps and databases.Faulting patterns near the caldera, extension directions derived from fault striae P and T axes, and three-dimensional temperature and alteration mineral models are consistent with slip across arcuate ring faults related to magma chamber deflation during flank eruptions and/or a pyroclastic eruption at about 180 ka. These results are not consistent with a rift or pull-apart basin. Limited subsidence can be attributed to the relatively small volume of ash-flow tuff released by the only known major pyroclastic eruption and is inconsistent with the observed topographic relief. The additional relief can be explained by constructional volcanism. Striae from unoriented and oriented core, augmented by striae measurements in outcrop suggest that Walker Lane dextral shear, which can be reasonably projected from the southeast, has probably propagated into the Medicine Lake area. Most volcanic vents across Medicine Lake Volcano strike northsouth, suggesting they are controlled by crustal weakness related to Basin and Range extension. Interaction of dextral shear, Basin and Range extension, and the zone of crustal weakness expressed as the Mount Shasta-Medicine Lake volcanic highland controlled the location and initiation of Medicine Lake Volcano at about 500 ka.

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Gravity anomalies, Quaternary vents, and Quaternary faults in the southern Cascade Range, Oregon and California: Implications for arc and backarc evolution

Cited by 52 publications

References 44 publications

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

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

Revised earthquake hazard of the Hat Creek fault, northern California: A case example of a normal fault dissecting variable-age basaltic lavas

Tectonic Versus Volcanic Origin of the Summit Depression at Medicine Lake Volcano, California

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