Download or read book Late Pleistocene Slip Rate for the Western Pinto Mountain Fault Morongo Valley Southern California written by Katherine Gabriel and published by . This book was released on 2017 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt: The San Gorgonio Pass (SGP) region of the San Andreas fault (SAF) system in southern California is complicated by overlapping, active strands and its intersection with prominent, secondary structures such as the Pinto Mountain fault (PMF). Recent work in this area proposes that strain may be transferred from the Mission Creek strand of the SAF to the Eastern California Shear Zone (ECSZ), at least partly via the PMF. Like the better known Garlock fault, the PMF is a major east-west trending left-lateral transverse fault that intersects the Mission Creek strand of the SAF in the eastern SGP area. Geodetic and geologic slip rates reported for the PMF vary from 1 to 12.5 mm/yr and are poorly constrained because of a lack of geologic data. This report describes a geologic slip rate from faulted alluvium in Big Morongo Canyon in Morongo Valley, California. A best-constrained strath contact between late Pleistocene alluvium (Qoa) and underlying bedrock (ggm) is offset in a left-lateral sense a total of 228 – 303 m. I obtained cosmogenic 10Be exposure ages of six monzo-granite boulders on the surface of Qoa. Assuming zero-erosion rate, boulder ages range from ~63 ka to ~88 ka. I believe that surface deflation and erosion has occurred, and therefore choose a weighted average of 86.9 +/- 4.5 ka as the preferred age for the surface of Qoa. I calculate a preferred slip rate of 3.0 +0.6/-0.4 mm/yr for western PMF system for the last ~87 ka. A fault scarp on one of the secondary splays in latest Pleistocene to Holocene alluvium (Qa) indicates that the western PMF has been active during the last
Download or read book Quaternary Slip History and Structural Analysis of the Morongo Valley Fault Morongo Valley CA written by James McNeil and published by . This book was released on 2018 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Morongo Valley Fault (MVF) is a northeast trending 18 km-long fault that is a splay from the overall sinistral Pinto Mountain Fault (PMF) system, located along Hwy 62 between Coachella Valley to the south and Yucca Valley to the north. Project results seek to constrain the role of the MVF with respect to the Coachella Valley SAF and Eastern California Shear Zone systems, and the hazard that rupture of this system poses to southern California residents. Mapping of the MVF reveals a series of en-echelon right step overs that resemble a sinistral extensional duplex. Uplifted terrace remnants of Quaternary alluvium occur to the SE of the fault, which dips northwest and is interpreted to be a left-oblique, normal fault system. A trench excavated across the MVF exposes strong evidence for one event at the bottom of the trench overlain by a colluvial wedge, and weak evidence for a second event at the top of the wedge. Calibrated radiocarbon ages from detrital charcoal constrain the first and possible second event to between 2,200-12,850 yrs BP. Three IRSL samples from the trench give much older ages (~20,000-116,000 yrs BP). The IRSL ages are not considered viable ages and probably carry an inheritance signal related to incomplete bleaching of feldspar grains. The trench site’s record of one, and possibly two, events since latest Pleistocene time suggests that the MVF ruptures infrequently relative to the Coachella Valley SAF system (average recurrence interval = ~220 yrs), and eastern PMF (at least four Holocene events). It is possible that the events on the MVF correlate with 1-2 events on eastern PMF. Alternatively, it is equally possible that the MVF breaks independently. The Eastern California Shear Zone (ECSZ) and 1992 Landers earthquake sequence may form the boundary between the eastern PMF, and MVF/western PMF. The paleoseismic record of the western PMF is unknown, but its geomorphic expression is similar to the MVF, and leads to speculation that the two faults possibly share a similar history. It seems likely, therefore that the MVF/western PMF act independently in the region. One explanation is that the SAF, PMF-MVF, and ECSZ form a triangle-shaped structural block at the southern Big Bend region of the SAF that acts as some form of crustal-scale 'ball-bearing' or pivot that accommodates slip transfer and gradients at the intersection of the SAF system and ECSZ. By itself, the MVF probably poses little seismic hazard to the region, but its location in the center of this complex region could mean that it breaks during or associated with rare events that involve multiple fault systems.
Download or read book High Geologic Slip Rates Since Early Pleistocene Initiation of the San Jacinto and San Felipe Fault Zones in the San Andreas Fault System Southern California USA written by and published by Geological Society of America. This book was released on 2010-01-01 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The San Jacinto right-lateral strike-slip fault zone is crucial for understanding plate-boundary dynamics, regional slip partitioning, and seismic hazards within the San Andreas fault system of southern California, yet its age of initiation and long-term average slip rate are controversial. This synthesis of prior and new detailed studies in the western Salton Trough documents initiation of structural segments of the San Jacinto fault zone at or slightly before the 1.07 Ma base of the Jaramillo subchron. In Special Paper 475, five new estimates of displacement are developed using offset successions of crystalline rocks; distinctive marker beds in the late Cenozoic basin fill; analysis of strike-slip-related fault-bend folds; quantification of strain in folds at the tips of dextral faults; and gravity, magnetic, and geomorphic data sets."--Publisher's website.
Download or read book Holocene Geologic Slip Rate for the Mission Creek Strand of the Southern San Andreas Fault Indio Hills written by Juan José Muñoz Zapata and published by . This book was released on 2017 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: Slip on the southern San Andreas fault in the northwestern Coachella Valley in Southern California is partitioned among three fault strands: the Mission Creek, Garnet Hill, and Banning strands. The NW-striking Mission Creek strand extends from the Indio Hills into the San Bernardino Mountains, whereas the Banning and Garnet Hill strands strike W-NW and transfer slip into the San Gorgonio Pass region. Together, these three faults accommodate ~ 20 mm/yr of right-lateral motion based on geodetic slip rate estimates. Determining which strand accommodates the majority of fault slip and how slip rates on these strands have varied over Quaternary timescales is critical to seismic hazard assessment for this region. Here I present a new Holocene geologic slip rate estimate from an offset alluvial fan complex along the Mission Creek fault at the Three Palms site in the Indio Hills. The correlation of offset fans precisely located from a satellite image, confirmed by field mapping and B4 LiDAR indicates that the Three Palms fan complex is offset 50.0 ± 5.0 meters. U-series dating on pedogenic carbonate rinds collected at 25-100 cm depth within the deposit constrain the minimum depositional age to 3.49 ± 0.92 ka (95% CI), yielding a maximum slip rate of 19.2 ± 2.0 mm/yr. Cosmogenic 10Be surface exposure dating on boulders yields a scattered dataset with high apparent inheritance and a median age of 13.6 +6.9/-6.7 ka (1[sigma] error). However, the minimum boulder age of 5.4 ± 1.0 ka (2[sigma] error) was interpreted as the maximum depositional age for the fan. This age, along with the preferred offset of 50.0 meters, yields a minimum slip rate of 7.8 ± 0.8 mm/yr. We therefore estimate a Holocene geologic slip rate of 7-21 mm/yr, with a preferred rate of 9-14 mm/yr. This rate overlaps within error with a previously published late Pleistocene slip rate on the Mission Creek strand of 12-22 mm/yr calculated at Biskra Palms Oasis a few kilometers to the southeast.
Download or read book Late Pleistocene Slip Rates Along the Panamint Valley Fault Zone Eastern California written by William R. Hoffman and published by . This book was released on 2009 with total page 89 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Panamint Valley fault zone (PVFZ) is one of the primary structures accommodating right lateral shear across the Eastern California Shear Zone. Current slip-rate estimates are either long-term estimates based on total offset of the system and bounds on the initiation of fault slip, or estimates that rely on undated alluvial deposits. Using field surveys and high-resolution airborne LiDAR digital topography, I utilize displaced alluvial deposits at two localities, Happy Canyon and Manly Peak Canyon, to provide new slip-rate estimates along the PVFZ. Chronologic control is provided by a newly developed chronosequence of soils in Panamint Valley, radiocarbon dating of lacustrine tufa associated with shoreline deposits, and terrestrial cosmogenic nuclide (10Be) dating of alluvial fan surfaces. At Manly Peak Canyon, debris flow levees offset 26.5 " 3.8 m with a maximum surface age of 12.5 " 1.4 ka yield a minimum extension rate of 2.1 " 0.5 mm/yr. At Happy Canyon, displaced alluvial markers demonstrate that slip along northeast-striking fault strands in the right-stepping portion of the fault zone is purely dip-slip with no lateral component. Here, an alluvial fan complex cut by a series of normal faults with total extension of 56.0 " 10.3 m has surface age estimates from a calibrated soil chronofunction ranging from ~16 - 40 ka, yielding a minimum extension rate of 2.7 " 1.5 mm/yr. Additionally, a 20.7 " 5.2 ka surface at Happy Canyon is cut by a fault scarp with 68.1 " 2.0 m of vertical offset, which yields a preliminary Late Pleistocene minimum throw rate of 3.3 " 0.7 mm/yr. Results from this thesis provide the only two slip-rate estimates along the PVFZ with chronologic control, and reveal along-strike variations in horizontal displacement direction that appear coordinated with increased subsidence in the northern part of the valley.
Download or read book Determination of Late Pleistocene Holocene Slip Rates Along the San Gregorio Fault Zone San Mateo County California written by Gerald Eric Weber and published by . This book was released on 1993 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Holocene Geologic Slip Rate for the Mission Creek Strand of the Southern San Andreas Fault CA written by Rosemarie C. Fryer and published by . This book was released on 2016 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: The San Andreas Fault is the primary structure accommodating relative plate motions between the Pacific and North American plates along the southwestern margin of North America. The northern San Andreas Fault (SAF) segment ruptured in 1906 and the central segment releases strain primarily by continuous creep. The south-central Mojave section of SAF ruptured in 1857, but the Coachella Valley section farthest south has not ruptured historically. The Coachella Valley section is therefore considered overdue for an earthquake because it has exceeded its average recurrence interval of ~150-200 years. In the northern Coachella Valley, the Southern SAF (SSAF) splays into three fault strands: the Mission Creek, Banning, and Garnet Hill strands. The NW-striking Mission Creek strand extends from the Indio Hills into the San Bernardino Mountains, whereas the Banning and Garnet Hill strands strike WNW and transfer slip into the San Gorgonio Pass region. Together, the three faults accommodate ~20 mm/yr of right-lateral motion based on geodetic measurements. Determining how slip is partitioned between these faults and how the slip rates have varied over different timescales is critical for southern California seismic hazard models. The purpose of this project was to establish a Holocene geologic slip rate for the Mission Creek strand of the SSAF at the Three Palms slip rate site in the southeast Indio Hills. At the Three Palms Site, located northwest of Biskra Palms, three alluvial fans sourced from three distinct catchments have been offset by the Mission Creek strand. The central portion of these fans is best preserved and records a right lateral displacement of ~57 ± 3 meters. Uranium-series dating of pedogenic carbonate rinds constrain the minimum depositional age of this fan. U-series dates give a standard corrected weighted mean average of 3.49 ± 0.92 ka, yielding a maximum slip rate of 16 +6.1/-3.8 mm/yr. Three samples from an individual clast give a nearly identical isochron age of 3.3 ± 0.6 ka, which provides confidence in the weighted average age. This Holocene maximum slip rate overlaps within error of the previously determined late Pleistocene slip rate measured at Biskra Palms of 12-22 mm/yr, suggesting that the Mission Creek strand slip rate has remained constant over these timescales and that it has remained the dominant fault accommodating slip at the southeast Indio Hills over the past ~50 kyr.
Download or read book High Geologic Slip Rates Since Early Pleistocene Initiation of the San Jacinto and San Felipe Fault Zones in the San Andreas Fault System Southern California USA written by Susanne U. Janecke and published by . This book was released on 2018 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pleistocene Slip Rate of the Owens Valley Fault California written by Matthew J. Rogers and published by . This book was released on 2006 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Temporal Variations in Slip rate Along the Lone Mountain Fault Western Nevada written by Jeffrey Simon Hoeft and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Late Pleistocene displacement along the Lone Mountain fault suggests the Silver Peak-Lone Mountain (SPLM) extensional complex is an important structure in accommodating and transferring strain within the eastern California shear zone (ECSZ) and Walker Lane. Using geologic and geomorphic mapping, differential global positioning system surveys, and terrestrial cosmogenic nuclide (TCN) geochronology, we determined rates of extension across the Lone Mountain fault in western Nevada. The Lone Mountain fault is the northeastern component of the SPLM extensional complex, and is characterized by a series of down-to-the-northwest normal faults that offset the northwestern Lone Mountain and Weepah Hills piedmonts. We mapped eight distinct alluvial fan deposits and dated three of the surfaces using ℗£1́ʻBE TCN geochronology, yielding ages of 16.5 +/- 1.2 ka, 92.3 +/- 8.6 ka, and 142.2 +/- 19.5 ka for the Q3b, Q2c, and Q2b deposits, respectively. The ages were combined with scarp profile measurements across the displaced fans to obtain minimum rates of extension; the Q2b and Q2c surfaces yield an extension rate between 0.1 +/- 0.1 and 0.2 +/- 01 mm/yr and the Q3b surface yields a rate of 0.2 +/-.1 to 0.4 +/- 0.1 mm/yr, depending on the dip of the fault. Active extension on the Lone Mountain fault suggests that it helps partition strain off of the major strike-slip faults in the northern ECSZ and transfers deformation around the Mina Deflection northward into the Walker Lane. Combining our results with estimates from other faults accommodating dextral shear in the northern ECSZ reveals an apparent discrepancy between short- and long-term rates of strain accumulation and release. If strain rates have remained constant since the late Pleistocene, this could reflect transient strain accumulation, similar to the Mojave segment of the ECSZ. However, our data also suggest an increase in strain rates between ~92 ka and ~17 ka, and possibly to present day, which may also help explain the mismatch between long- and short-term rates of deformation in the region.
Download or read book The Owens Valley Fault Zone Eastern California and Surface Faulting Associated with the 1872 Earthquake written by Sarah Beanland and published by . This book was released on 1994 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: Estimates of slip and magnitude of the 1872 Owens Valley earthquake and estimates of late Quaternary slip, slip rate, and earthquake recurrence associated with the 100-km-long fault zone as determined at 40 sites.
Download or read book Mojave Desert written by and published by . This book was released on 1994 with total page 692 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Determination of Paleoearthquake Age and Slip Per Event Data and Late Pleistocene Holocene Slip Rates on a Blind thrust Fault written by Shari A. Christofferson and published by . This book was released on 2002 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Old Routes to the Colorado written by Jennifer Reynolds and published by . This book was released on 1992 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: 21 essays
Download or read book Slip Rate and Earthquake History of the Northern San Gregorio Fault Zone Near Seal Cove California written by Gary D. Simpson and published by . This book was released on 1998 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Neotectonics of the Western Reach of the Agua Blanca Fault Baja California Mexico written by David Lynn Schug and published by . This book was released on 1987 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Late Holocene Slip Rate and Amounts of Coseismic Rupture Along the Central Calavaras Fault San Francisco Bay Area California written by Keith Irvin Kelson and published by . This book was released on 1998 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
