Preliminary Isostatic Gravity Map of Joshua Tree National Park and Vicinity, Southern California

Langenheim, Victoria E.; Biehler, Shawn; McPhee, D. K.; McCabe, Craig A.; Watt, Janet T.; Anderson, MaryAnn; Chuchel, Bruce A.; Stoffer, Philip W.

doi:10.3133/ofr20071218

Cited by 7 publications

(7 citation statements)

References 6 publications

(6 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Methods include compilation of previously published and unpublished geologic maps, mapping and observations of fault-scarp morphol-Dorsey and Langenheim | Tilting of the Salton block, southern California GEOSPHERE | Volume 11 | Number 5 ogy, measurement of fault-zone fabrics, quantitative geomorphic analysis in ArcMap (http:// www .esri .com /software /arcgis) using 30 m digital elevation models (DEMs), and measurement of alluvial fan and corresponding catchment areas on DEMs and satellite imagery. Gravity data (Biehler et al, 1992;Langenheim et al, 2005Langenheim et al, , 2007Martin et al, 1997;Langenheim, 2008, personal data) were used to examine basin geometry using two different methods. Depth of subsurface basins throughout the region of Figure 1 was modeled through 3-D inversion of gravity data using the method of Jachens and Moring (1990) and parameters in Langenheim et al (2005;see following).…”

Section: Methodsmentioning

confidence: 99%

Crustal-scale tilting of the central Salton block, southern California

Dorsey

Langenheim

2015

Geosphere

View full text Add to dashboard Cite

The southern San Andreas fault system (California, USA) provides an excellent natural laboratory for studying the controls on vertical crustal motions related to strike-slip deformation. Here we present geologic, geomorphic, and gravity data that provide evidence for active northeastward tilting of the Santa Rosa Mountains and southern Coachella Valley about a horizontal axis oriented parallel to the San Jacinto and San Andreas faults. The Santa Rosa fault, a strand of the San Jacinto fault zone, is a large southwest-dipping normal fault on the west flank of the Santa Rosa Mountains that displays well-developed triangular facets, narrow footwall canyons, and steep hanging-wall alluvial fans. Geologic and geomorphic data reveal ongoing footwall uplift in the southern Santa Rosa Mountains, and gravity data suggest total vertical separation of ~5.0-6.5 km from the range crest to the base of the Clark Valley basin. The northeast side of the Santa Rosa Mountains has a gentler topographic gradient, large alluvial fans, no major active faults, and tilted inactive late Pleistocene fan surfaces that are deeply incised by modern upper fan channels. Sediments beneath the Coachella Valley thicken gradually northeast to a depth of ~4-5 km at an abrupt boundary at the San Andreas fault. These features all record crustal-scale tilting to the northeast that likely started when the San Jacinto fault zone initiated ca. 1.2 Ma. Tilting appears to be driven by oblique shortening and loading across a northeast-dipping southern San Andreas fault, consistent with the results of a recent boundary-element modeling study.

show abstract

Section: Methodsmentioning

confidence: 99%

Crustal-scale tilting of the central Salton block, southern California

Dorsey

Langenheim

2015

Geosphere

View full text Add to dashboard Cite

show abstract

“…Gravity data reveal northeastward thickening of sediments in the Coachella Valley, suggesting increased subsidence to the northeast (Langenheim et al, 2005;Langenheim et al, 2007). Exposure of Pliocene marine deposits at high elevation in the southern Santa Rosa Mountains requires post-Pliocene uplift of at least ~600 m (Matti et al, 2002).…”

Section: Deformation In the Coachella Valleymentioning

confidence: 99%

“…Steep range front morphology, prominent fault facets, large landslides on the faulted western fl ank of the Santa Rosa Mountains, and the presence of large alluvial fans on the eastern fl ank record signifi cant asymmetric tilting to the northeast . An abrupt subvertical discontinuity in the thickness of subsurface sediment at the San Andreas fault, from several kilometers on the southwest side to <1 km on the northeast side (Langenheim et al, 2007;Fuis et al, 2012) implies relative subsidence on the southwest side of the Coachella Valley segment of the San Andreas fault.…”

Section: Deformation In the Coachella Valleymentioning

confidence: 99%

Sensitivity of uplift patterns to dip of the San Andreas fault in the Coachella Valley, California

2014

View full text Add to dashboard Cite

Three-dimensional mechanical simulations of the San Andreas fault system within the Coachella Valley in southern California produce deformation that matches geologic observations and demonstrate the firstorder impact of fault geometry on uplift patterns. To date, most models that include the Coachella Valley segment of the San Andreas fault have assumed a vertical orientation for this fault, but recent studies of seismicity and geodetically observed strain suggest that this segment of the fault may dip 60°-70° to the northeast. We compare models with varied geometry along this segment of the fault and evaluate how well they reproduce observed uplift patterns in the Mecca Hills and Coachella Valley. Incorporating wellconstrained fault geometry in regional models will provide a more accurate understanding of active faulting in southern California, which is critical for rupture and hazard modeling that is used to identify regions most susceptible to earthquake damage.We have tested three boundary-element method models for the active geometry of the Coachella Valley segment of the San Andreas fault: one contains a vertical Coachella segment, the second contains a northeast ~65° dipping Coachella segment, and the fi nal alternative contains a vertical Coachella segment plus a subparallel northeast-dipping fault at depth. This fi nal model honors the geometric interpretation of seismicity from the Southern California Earthquake Center Community Fault Model version 4.0. The models containing vertical Coachella Valley segments both produce uplift between the San Andreas and San Jacinto faults that is more uniformly distributed than geologic observations suggest, and these models fail to produce uplift in the Mecca Hills. The dipping model produces tilting of the Coachella Valley consistent with geologic observations of tilting between the San Jacinto and San Andreas faults. The dipping model also produces relative subsidence southwest of the fault and localized uplift in the Mecca Hills that better match the geologic observations. These results suggest that the active Coachella Valley segment of the San Andreas fault dips 60°-70° to the northeast.

show abstract

“…This class of uncertainty may be appreciable for regions characterized by diffuse networks of faults, such as in the ETR and ECSZ regions. Therefore, to assess the effects of fault‐block geometries on our slip‐rate estimates we investigate four different fault‐block scenarios (Figures 7, 8, 9, and 10) that incorporate the major faults [ Jennings , 1994] in the region, as well as faults inferred from interpretation of a published isostatic residual gravity map [ Langenheim et al , 2007] and the pattern of instrumentally recorded seismicity [ Southern California Earthquake Data Center , 2010]. Below we will treat these different models as working hypotheses, exploring their implications for fault slip rate in light of the geodetic velocity field.…”

Section: Fault Slip Estimationmentioning

confidence: 99%

Present‐day strain accumulation and slip rates associated with southern San Andreas and eastern California shear zone faults

et al. 2010

View full text Add to dashboard Cite

[1] We present the first results from a dense network of 36 campaign and 46 continuous GPS stations located in the Eastern Transverse Ranges Province (ETR), a transition zone between the southernmost San Andreas fault (SSAF) and eastern California shear zone (ECSZ). We analyzed the campaign data together with available data from continuous GPS stations for the period 1994-2009. We used the GPS velocity estimates to constrain elastic block models to investigate fault-loading rates representing four hypotheses characterized by different fault-block geometries. Fault-block scenarios include blocks bounded by the east-striking left-lateral Pinto Mountain, Blue Cut, and Chiriaco faults of the ETR; blocks bounded by a right-lateral north-northwest striking structure (the "Landers-Mojave earthquake line") that cuts obliquely across the ETR and mapped Mojave Desert faults; and combinations of these end-member hypotheses. Each model implies significantly different active fault geometries, block rotation rates, and slip rates for ETR and ECSZ structures. All models suggest that SSAF slip rate varies appreciably along strike, generally consistent with rates derived from tectonic geomorphology and paleoseismology, with a maximum of ∼23 mm/yr right-lateral along the southernmost Coachella Valley strand, decreasing systematically to <10 mm/yr right-lateral through the San Gorgonio Pass region. Slip rate estimates for the San Jacinto fault are ∼12 mm/yr for all models tested. All four models fit the data equally well in a statistical sense. Qualitative comparison among models and consideration of geologic slip rates and other independent data reveals strengths and weaknesses of each model.

show abstract

Preliminary Isostatic Gravity Map of Joshua Tree National Park and Vicinity, Southern California

Abstract: Gravity anomaly contours. Contour interval, 2 mGal. Hachures indicate gravity low. Contours were computergenerated based on a 300-m grid. Although the data have been edited, caution should be exercised when interpreting anomalies controlled by only a single gravity station.

Cited by 7 publications

References 6 publications

Crustal-scale tilting of the central Salton block, southern California

Crustal-scale tilting of the central Salton block, southern California

Sensitivity of uplift patterns to dip of the San Andreas fault in the Coachella Valley, California

Present‐day strain accumulation and slip rates associated with southern San Andreas and eastern California shear zone faults

Contact Info

Product

Resources

About