TY - JOUR A1 - Ortiz, Gustavo A1 - Saez, Mauro A1 - Alvarado, Patricia A1 - Rivas, Carolina A1 - García, Víctor Hugo A1 - Alonso, Ricardo A1 - Zullo, Fernando Morales T1 - Seismotectonic characterization of the 1948 (M-W 6.9) Anta earthquake Santa Barbara System, central Andes broken foreland of northwestern Argentina JF - Journal of South American earth sciences N2 - The region of the Andean back-arc of northwestern Argentina has been struck by several magnitude >= 6 crustal earthquakes since the first historically recorded event in 1692. One of these events corresponds to the Anta earthquake on 25 August 1948, with epicenter in the Santa Barbara System causing three deaths and severe damage in Salta and Jujuy provinces with maximum Modified Mercalli seismic intensities (MMI) of IX. We collected and digitized analog seismograms of this earthquake from worldwide seismic observatories in order to perform first-motion analysis and modeling of long-period teleseismic P-waveforms. Our results indicate a simple seismic source of M0 = 2.85 x 1019 N m consistent with a moment magnitude Mw = 6.9. We have also tested for the focal depth determining a shallow source at 8 km with a reverse focal mechanism solution with a minor dextral strike-slip component (strike 20 degrees, dip 30 degrees, rake 120 degrees) from the best fit of waveforms. Using magnitude size empirical relationships, the comparison of the obtained Mw 6.9 magnitude value and the ca. 10,000 km2 area of MMI >= IX from our seismic intensity map, which was obtained from newspaper and many historical reports, indicates a rupture length of 42 +/- 8 km for the Anta earthquake. We show our results in a 3D geological model around the epicentral area, which integrates modern seismicity, geological data, and information of a previously studied east-west cross section located a few kilometers south of the 1948 epicenter. The integration of all available information provides evidence of the re-activation of the Pie de la Sierra del Gallo fault during the 1948 Mw 6.9 shallow earthquake; this thrust fault bounds the Santa Barbara System along its western foothill. KW - Active tectonics KW - Analog historical seismograms KW - Andean back-arc; KW - Thick-skinned tectonics KW - Central Andes Y1 - 2022 U6 - https://doi.org/10.1016/j.jsames.2022.103822 SN - 0895-9811 SN - 1873-0647 VL - 116 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Gao, Mingxing A1 - Zeilinger, Gerold A1 - Xu, Xiwei A1 - Wang, Qingliang A1 - Hao, Ming T1 - DEM and GIS analysis of geomorphic indices for evaluating recent uplift of the northeastern margin of the Tibetan Plateau, China JF - Geomorphology : an international journal on pure and applied geomorphology N2 - The northeastern margin of the Tibetan Plateau is a tectonically active region consisting of a series of faults with bounded intermountain basins and is located in the transition zone between the Tibetan Plateau and the Loess Plateau. Active deformation that may affect the topography in this region can be quantified using geomorphic indices. Therefore, we applied geomorphic indices such as the hypsometric integral and the stream length gradient index to infer neo-tectonics in the northeastern margin of the Tibetan Plateau. Different time-scaled geodetic leveling data and river incision rates were also integrated into the investigation. The results show that the hypsometric integrals are not significantly affected by lithology but spatially correspond to the hanging walls of thrust faults. The hypsometric integrals are also positively correlated with the leveling data. Although the stream length gradient index is influenced by lithology, its most pronounced anomalies of the stream length gradient are associated with the thrust faults. Consequently, the uplift in the northeast margin of the Tibetan Plateau appeared to be concentrated along the hanging walls of the thrust faults. KW - Tectonic geomorphology KW - Hypsometry analysis KW - Stream length gradient KW - Active tectonics KW - Leveling data KW - Tibetan Plateau Y1 - 2013 U6 - https://doi.org/10.1016/j.geomorph.2013.02.008 SN - 0169-555X VL - 190 IS - 20 SP - 61 EP - 72 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kirby, Eric A1 - Harkins, Nathan T1 - Distributed deformation around the eastern tip of the Kunlun fault JF - INTERNATIONAL JOURNAL OF EARTH SCIENCES N2 - Whether active strain within the Indo-Asian collision zone is primarily localized along major strike-slip fault systems or is distributed throughout the intervening crust between faults remains uncertain. Despite refined estimates of slip rates along many of the major fault zones, relatively little is known about how displacement along these structures is accommodated at fault terminations. Here, we show that a systematic decrease in left-lateral slip rates along the eastern similar to 200 km of the Kunlun fault, from > 10 mm/year to < 1 mm/year, is coincident with high topography in the Anyemaqen Shan and with a broad zone of distributed shear and clockwise vorticity within the Tibetan Plateau. Geomorphic analysis of river longitudinal profiles, coupled with inventories of cosmogenic radionuclides in fluvial sediment, reveal correlated variations in fluvial relief and erosion rate across the Anyemaqen Shan that reflect ongoing differential rock uplift across the range. Our results imply that the termination of the Kunlun fault system is accommodated by a combination of distributed crustal thickening and by clockwise rotation of the eastern fault segments. KW - Tibetan plateau KW - Active tectonics KW - Tectonic geomorphology KW - Strike-slip faults Y1 - 2013 U6 - https://doi.org/10.1007/s00531-013-0872-x SN - 1437-3254 SN - 1437-3262 VL - 102 IS - 7 SP - 1759 EP - 1772 PB - SPRINGER CY - NEW YORK ER -