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Jean Philippe Avouac - One of the best experts on this subject based on the ideXlab platform.
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denudation outpaced by crustal thickening in the eastern tianshan
Earth and Planetary Science Letters, 2017Co-Authors: Julien Charreau, Jean Philippe Avouac, Dimitri Saintcarlier, Stephane Dominguez, Jerome Lave, Pierrehenri Blard, Marc Jolivet, Yan Chen, Shengli Wang, Nathan D BrownAbstract:The modern high topography of the Tianshan resulted from the reactivation of a Paleozoic orogenic belt by the India/Asia collision. Today, the range exhibits tectonically active forelands and intermontane basins. Based on quantitative morphotectonic observations and age constraints derived from cosmogenic 10Be dating, single-grain post-infrared infrared stimulated luminescence (p-IR IRSL) dating and modeling of Fault Scarp degradation, we quantify the deformation in the Nalati and Bayanbulak intermontane basins in the central Eastern Tianshan. Our results indicate that at least 1.4 mm/yr of horizontal crustal shortening is accommodated within these two basins. This shortening represents over 15% of the 8.5 ± 0.5 mm/yr total shortening rate across the entire range at this longitude. This shortening rate implies that the Eastern Central Tianshan is thickening at a mean rate of ∼1.4 mm/yr, a rate that is significantly higher than the average denudation rate of 0.14 mm/yr derived from our cosmogenic analysis. This discrepancy suggests that the Tianshan range has not yet reached a steady-state topography and remains in a transient state of topographic growth, most likely due to limited denudation rates driven by the arid climate of Central Asia.
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active tectonics in southern xinjiang china analysis of terrace riser and normal Fault Scarp degradation along the hotan qira Fault system
Journal of Geophysical Research, 1993Co-Authors: Jean Philippe Avouac, Gilles PeltzeAbstract:The northern piedmont of the western Kunlun mountains (Xinjiang, China) is marked at its easternmost extremity, south of the Hotan-Qira oases, by a set of normal Faults trending N50E for nearly 70 km. Conspicuous on Landsat and SPOT images, these Faults follow the southeastern border of a deep flexural basin and may be related to the subsidence of the Tarim platform loaded by the western Kunlun northward overthrust. The Hotan-Qira normal Fault system vertically offsets the piedmont slope by 70 m. Highest Fault Scarps reach 20 m and often display evidence for recent reactivations about 2 m high. Successive stream entrenchments in uplifted footwalls have formed inset terraces. We have leveled topographic profiles across Fault Scarps and transverse abandoned terrace risers. The state of degradation of each terrace edge has been characterized by a degradation coefficient τ, derived by comparison with analytical erosion models. Edges of highest abandoned terraces yield a degradation coefficient of 33 ± 4 m^2. Profiles of cumulative Fault Scarps have been analyzed in a similar way using synthetic profiles generated with a simple incremental Fault Scarp model. The analysis shows that (1) rate of Fault slip remained essentially constant since the aggradation of the piedmont surface and (2) the occurrence of inset terraces was synchronous at all studied sites, suggesting a climate-driven terrace formation. Observation of glacial and periglacial geomorphic features along the northern front of the western Kunlun range indicates that the Qira glaciofluvial fan emplaced after the last glacial maximum, during the retreat of the Kunlun glaciers (12–22 ka). The age of the most developed inset terrace in uplifted valleys is inferred to be 10 ± 3 ka, coeval with humid climate pulses of the last deglaciation. The mass diffusivity constant (k=τ/T, being time B.P.) in the Hotan region is determined to be 3.3 ± 1.4 m^2/10^3 years, consistent with other estimates in similar climatic and geologic environments of western China. These results imply a minimum rate for the Tarim subsidence of 3.5 ± 2 mm/yr. If Western Kunlun overthrusts the Tarim platform on a crustal ramp dipping 40°–45° to the south, it would absorb at least 4.5 ± 3 mm/yr of convergence between western Tibet and Tarim.
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active tectonics in southern xinjiang china analysis of terrace riser and normal Fault Scarp degradation along the hotan qira Fault system
Journal of Geophysical Research, 1993Co-Authors: Jean Philippe Avouac, Gilles PeltzerAbstract:The northern piedmont of the western Kunlun mountains (Xinjiang, China) is marked at its easternmost extremity, south of the Hotan-Qira oases, by a set of normal Faults trending N50E for nearly 70 km. Conspicuous on Landsat and SPOT images, these Faults follow the southeastern border of a deep flexural basin and may be related to the subsidence of the Tarim platform loaded by the western Kunlun northward overthrust. The Hotan-Qira normal Fault system vertically offsets the piedmont slope by 70 m. Highest Fault Scarps reach 20 m and often display evidence for recent reactivations about 2 m high. Successive stream entrenchments in uplifted footwallls have formed inset terraces. We have leveled topographic profiles across Fault Scarps and transverse abandoned terrace risers. The state of degradation of each terrace edge has been characterized by a degradation coefficient tau, derived by comparison with analytical erosion models. Edges of highest abandoned terraces yield a degradation coefficient of 33 +/- 4 sq.m. Profiles of cumulative Fault Scarps have been analyzed in a similar way using synthetic profiles generated with a simple incremental Fault Scarp model.
James P Mccalpin - One of the best experts on this subject based on the ideXlab platform.
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differentiating between gravitational and tectonic Faults by means of geomorphological mapping trenching and geophysical surveys the case of the zenzano Fault iberian chain n spain
Geomorphology, 2013Co-Authors: Domingo Carbonel, James P Mccalpin, Francisco Gutierrez, Rogelio Linares, Carles Roque, Mario Zarroca, Jesus Guerrero, V RodriguezAbstract:Abstract The Zenzano Fault Scarp has been developed on the top of a 475 m-high erosional eScarpment underlain by an upper brittle sequence and a lower halite-bearing evaporitic formation. The 1850 m-long Fault, with a maximum displacement of 45 m and parallel to the eScarpment, has offset the back of a dip slope, generating an antislope Scarp with prominent triangular facets up to 38 m high and obstructing consequent transverse drainages (defeated streams). Both gravitational and tectonic interpretations were previously proposed for this active surface rupture. The Fault Scarp has been investigated by detailed geological and geomorphological mapping, geophysical surveys (GPR and ERT) and two trenches excavated across the Fault in disrupted drainages. The geophysical profiles clearly imaged the Fault, helping to site the trenches and roughly estimate the thickness of the deposits accumulated in the downthrown block. Although the maximum displacement to length ratio (Dmax/L) of the Fault fall within the range of tectonic Faults of similar length, according to the world database, the geological and geomorphological context, together with several parameters reveal that this structure corresponds to a gravitational failure: (1) anomalously high vertical displacement per event (> 1.4 m); (2) high apparent vertical slip rate (~ 0.6 mm/year); and (3) short recurrence interval of Faulting events. The negligible horizontal displacement component on the dip-slip Fault, as well as the presence of very large caprock collapse sinkholes and saline springs, strongly suggest that interstratal karstification of the halite-bearing evaporites has played a primary role in the development of the gravitational failure. The formation of this morphostructure has been favoured by pre-existing tectonic Faults, erosional unloading related to the removal of an overburden ca. 800 m thick, and enhanced groundwater recharge due to the blockage of the drainage. This work illustrates that the proposed multidisciplinary approach allows the identification of features and calculation of parameters that may help to elucidate whether an active failure has a gravitational or a tectonic origin.
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2001 bhuj kachchh earthquake surface Faulting and its relation with neotectonics and regional structures gujarat western india
Annals of Geophysics, 2009Co-Authors: James P Mccalpin, M G ThakkarAbstract:Primary and secondary surface deformation related to the 2001 Bhuj-Kachchh earthquake suggests that thrusting movement took place along an E-W Fault near the western extension of the South Wagad Fault, a synthetic Fault of the Kachchh Mainland Fault (KMF). Despite early reconnaissance reports that concluded there was no primary surface Faulting, we describe an 830 m long, 15-35 cm high, east-west-trending thrust Fault Scarp near where the seismogenic Fault plane would project to the surface, near Bharodiya village (between 23°34.912vN, 70°23.942vE and 23°34.304vN, 70°24.884vE). Along most of the Scarp Jurassic bedrock is thrust over Quaternary deposits, but the Fault Scarp also displaces Holocene alluvium and an earth dam, with dips of 13° to 36° south. Secondary co-seismic features, mainly liquefaction and lateral spreading, dominate the area south of the thrust. Transverse right-lateral movement along the «Manfara Fault» and a parallel Fault near Bharodiya suggests segmentation of the E-W master Faults. Primary (thrust) surface rupture had a length of 0.8 km, maximum displacement of about 35 cm, and average displacement of about 15 cm. Secondary (strike-slip) Faulting was more extensive, with a total end-to-end length of 15 km, maximum displacement of 35 cm, and average displacement of about 20 cm.
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sedimentology of Fault Scarp derived colluvium from the 1983 borah peak rupture central idaho
Journal of Sedimentary Research, 1993Co-Authors: James P Mccalpin, Witold Zuchiewicz, L Allen C JonesAbstract:ABSTRACT Ten undisturbed samples of Scarp-derived colluvium from the 1983 Borah Peak, Idaho, Fault Scarp were subjected to laboratory grain-size and fabric measurements to characterize typical colluvium from a Basin and Range Fault Scarp. Colluvial deposits consisted of poorly-sorted pebble gravels (mean diameter -0.3 to -3.75 ; 1.2 to 13.5 mm) with 25-79% matrix (< 4 mm). Stereograms of long-axis orientations of 115 clasts from each colluvial wedge yielded girdle-type distributions, with typical eigenvalue ratios of In S1/S2 = 0.05-0.50 and In S2/S3 = 0.3-1.0 These girdle distributions indicate preferred orientation in angle-of-repose planes coincident with colluvial wedge depositional planes. Short-axis stereograms display single or du l maxima with mean bearing parallel to transport direction and plunge perpendicular to the colluvial wedge surface. Clast fabric strength is not strongly correlated with Scarp aspect (corr. coeff. = 0.03 to 0.68) or with the slope of the Faulted geomorphic surface (corr. coeff. = -0.16 to +0.57), but it improves with increasing matrix content (corr. coeff. = -0.04 to -0.42). Fabrics in measured wedges are weaker than those reported for other colluviums and talus and resemble fabrics in debris flows. However, the stronger girdle tendencies and distinct orientation subgroups in Scarp-derived colluvium should distinguish it from suspected debris flow deposits in Fault-zone exposures.
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thermoluminescence dating of Fault Scarp derived colluvium deciphering the timing of paleoearthquakes on the weber segment of the wasatch Fault zone north central utah
Journal of Geophysical Research, 1991Co-Authors: Steven L Forman, Alan R. Nelson, James P MccalpinAbstract:The timing of middle to late Holocene Faulting on the Weber segment of the Wasatch Fault zone, Utah, is constrained by thermoluminescence (TL) and radiocarbon age estimates on fine-grained, Fault-related colluvial sediments. The stratigraphy in two trenches excavated across Fault Scarps is characterized by a stack of three colluvial wedges, deposited in response to three separate Faulting events, the oldest of which buried a soil developed on a middle Holocene debris flow. Thermoluminescence age estimates by the partial and total bleach methods and the regeneration method on fine-grained colluvium from the trenches agree within 1 sigma and are concordant with the radiocarbon chronology. A synthesis of the TL and 14C age estimates indicate that these three Faulting events occurred sometime between 4500 and 3500, between 3200 and 2500, and between 1400 and 1000 years ago. Detailed investigation of a sequence of fine-grained, Scarp-derived distal colluvium shows that much of the sediment was deposited during <600-year intervals immediately after Faulting. The sedimentation rate of colluvium is inferred to increase shortly after Faulting, and TL dating of these sediments provides additional information to constrain the timing of Faulting events.
Gilles Peltzer - One of the best experts on this subject based on the ideXlab platform.
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active tectonics in southern xinjiang china analysis of terrace riser and normal Fault Scarp degradation along the hotan qira Fault system
Journal of Geophysical Research, 1993Co-Authors: Jean Philippe Avouac, Gilles PeltzerAbstract:The northern piedmont of the western Kunlun mountains (Xinjiang, China) is marked at its easternmost extremity, south of the Hotan-Qira oases, by a set of normal Faults trending N50E for nearly 70 km. Conspicuous on Landsat and SPOT images, these Faults follow the southeastern border of a deep flexural basin and may be related to the subsidence of the Tarim platform loaded by the western Kunlun northward overthrust. The Hotan-Qira normal Fault system vertically offsets the piedmont slope by 70 m. Highest Fault Scarps reach 20 m and often display evidence for recent reactivations about 2 m high. Successive stream entrenchments in uplifted footwallls have formed inset terraces. We have leveled topographic profiles across Fault Scarps and transverse abandoned terrace risers. The state of degradation of each terrace edge has been characterized by a degradation coefficient tau, derived by comparison with analytical erosion models. Edges of highest abandoned terraces yield a degradation coefficient of 33 +/- 4 sq.m. Profiles of cumulative Fault Scarps have been analyzed in a similar way using synthetic profiles generated with a simple incremental Fault Scarp model.
Iain S Stewart - One of the best experts on this subject based on the ideXlab platform.
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normal Fault zone evolution and Fault Scarp degradation in the aegean region
Basin Research, 2007Co-Authors: Iain S Stewart, P L HancockAbstract:The initial stages of rift-basin evolution are periods of great landform change. Fault Scarps are newly created axes of erosion which, along with footwall uplands, act as sediment sources for subsiding hanging wall basins. Scarps formed during neotectonic normal Faulting of Mesozoic carbonates in mainland Greece and western Turkey display a varied pattern of degradation related to the history of Fault development and variations in Fault zone architecture. Alternating zone-parallel compact breccia sheets and incohesive breccia belts, of contrasting resistance to erosion, underlie Scarps. Meso-scale slip-plane phenomena, such as corrugations, gutters, comb fractures, and pluck holes, together with geomorphological features, such as subsurface solution pipes, and vegetation result in initial variations in the denudability of erosionally resistant compact breccia sheets. Migration with time of slip-plane activity within a Fault zone into its hanging wall (i.e. intraFault-zone hanging wall collapse) adds to the structural heterogeneity of Fault Scarp footwalls. Quaternary talus, whether of€set across a Fault, banked unconformably against a slip plane, or Faulted against a reactivated slip plane, has a dampening effect on degradation. The complexities of Fault zone architecture combined with a history of hanging wall collapse lead, in the Aegean region, to non-uniform degradation and Scarps which are commonly stepped and occasionally cavitated.
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dating recent colluvial sequences with 210pb and 137cs along an active Fault Scarp the eliki Fault gulf of corinth greece
Tectonophysics, 2004Co-Authors: Andrew B Cundy, Iain S StewartAbstract:Reliable dating is an essential element of palaeoseismological studies, yet whilst a suite of geochronological methods can now provide late Quaternary age control it remains very difficult to date modern events (i.e., those occurring within the last 150 years). This is significant because the starting point for many palaeoseismological investigations is a modern surface-rupturing event, whose geological effects need to be disentangled in trench stratigraphies from palaeoseismic ruptures. Two dating methods which, in combination, can provide robust dating control in recently deposited sediments are the 210Pb and 137Cs dating methods. Here, we test the applicability of using 210Pb and 137Cs to date colluvial sediments exposed in three trenches excavated across an earthquake Fault—the Eliki Fault, Gulf of Corinth, Greece—which ruptured in an earthquake in 1861. The 210Pb and 137Cs profiles observed in these colluvial sequences are relatively erratic due to the mixed nature of the sediments, i.e., their deposition in an environment where the supply of slope sediments is driven by seasonal rainfall, causing non-uniform sediment accretion and sediment reworking. In one trench, however, 210Pb dating, corroborated by 137Cs dating, indicates that a proposed post-1861 surface colluvial unit has been deposited over the period 1950 AD–present (at a rate of ca. 9 mm/year), and overlies a significantly older unit (>120 years old). The dating control provided here by 210Pb and 137Cs dating corroborates the published interpretation of the trench stratigraphy, and refines the 14C-based estimated dates for the upper unit. At two other trenches 210Pb and 137Cs dating only provided minimum ages (based on the presence or absence of 210Pbexcess and 137Cs). Such approximate ages, however, may still useful in corroborating interpretations made using the trench stratigraphy, or, at sites which have long earthquake recurrence intervals, determining which earthquake event was responsible for a particular bed offset.
Gilles Peltze - One of the best experts on this subject based on the ideXlab platform.
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active tectonics in southern xinjiang china analysis of terrace riser and normal Fault Scarp degradation along the hotan qira Fault system
Journal of Geophysical Research, 1993Co-Authors: Jean Philippe Avouac, Gilles PeltzeAbstract:The northern piedmont of the western Kunlun mountains (Xinjiang, China) is marked at its easternmost extremity, south of the Hotan-Qira oases, by a set of normal Faults trending N50E for nearly 70 km. Conspicuous on Landsat and SPOT images, these Faults follow the southeastern border of a deep flexural basin and may be related to the subsidence of the Tarim platform loaded by the western Kunlun northward overthrust. The Hotan-Qira normal Fault system vertically offsets the piedmont slope by 70 m. Highest Fault Scarps reach 20 m and often display evidence for recent reactivations about 2 m high. Successive stream entrenchments in uplifted footwalls have formed inset terraces. We have leveled topographic profiles across Fault Scarps and transverse abandoned terrace risers. The state of degradation of each terrace edge has been characterized by a degradation coefficient τ, derived by comparison with analytical erosion models. Edges of highest abandoned terraces yield a degradation coefficient of 33 ± 4 m^2. Profiles of cumulative Fault Scarps have been analyzed in a similar way using synthetic profiles generated with a simple incremental Fault Scarp model. The analysis shows that (1) rate of Fault slip remained essentially constant since the aggradation of the piedmont surface and (2) the occurrence of inset terraces was synchronous at all studied sites, suggesting a climate-driven terrace formation. Observation of glacial and periglacial geomorphic features along the northern front of the western Kunlun range indicates that the Qira glaciofluvial fan emplaced after the last glacial maximum, during the retreat of the Kunlun glaciers (12–22 ka). The age of the most developed inset terrace in uplifted valleys is inferred to be 10 ± 3 ka, coeval with humid climate pulses of the last deglaciation. The mass diffusivity constant (k=τ/T, being time B.P.) in the Hotan region is determined to be 3.3 ± 1.4 m^2/10^3 years, consistent with other estimates in similar climatic and geologic environments of western China. These results imply a minimum rate for the Tarim subsidence of 3.5 ± 2 mm/yr. If Western Kunlun overthrusts the Tarim platform on a crustal ramp dipping 40°–45° to the south, it would absorb at least 4.5 ± 3 mm/yr of convergence between western Tibet and Tarim.
