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Item type:Publication, First record of OSL‐dated fluvial sands in a tropical Andean cave reveals rapid late Quaternary tectonic uplift(Wiley, 2020-12-05)Abstract We present the first results of OSL‐dated fluvial sands extracted from a riverside cave in the tropical Andes. The excellent agreement between the ages of the various samples allowed the calculation of a late Quaternary valley incision rate forced by ongoing uplift of an active Subandean fault‐propagation fold in NE Peru. A structural cross‐section was constructed to understand the relationship between the geometry of the fault‐propagation fold, historical damaging earthquakes and the cave system. The calculated uplift rate is 2.3 to 2.6 mm a−1 over the past 70 ka and can be directly linked to active propagation of west‐verging basement thrusts. It is similar to uplift rates calculated from fluvial terraces in the Subandes of Colombia and Venezuela. The results will help to better assess the seismic hazard and confirm that OSL dating of fluvial sands in caves is a powerful tool to quantify uplift rates of active mountain fronts. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Earthquake surface ruptures on the altiplano and geomorphological evidence of normal faulting in the December 2016 (Mw 6.1) Parina earthquake, Peru(Elsevier, 2020-12-13)The 2016 Mw 6.1 Parina earthquake ruptured a shallow-crustal normal fault within the high Andes of south Peru. We use high-resolution DEMs and field mapping of the surface ruptures generated by the earthquake, in combination with co-seismic and post-seismic InSAR measurements, to investigate how different features of the geomorphology at Parina are generated by the earthquake cycle on the Parina Fault. We systematically mapped 12 km of NW-SE trending surface ruptures with up to ~27 cm vertical displacement and ~25 cm tensional opening along strike, separated by a gap with no observable surface ruptures. Co- and post-seismic InSAR measurements require slip below this gap in surface ruptures, implying that surface offsets observed in paleoseismic trenches may not necessarily be representative of slip at seismogenic depths, and will typically yield an underestimate of paleo-earthquake magnitudes. The surface ruptures developed along 10–20 m high cumulative scarps cutting through late Quaternary fluvio-glacial deposits and bedrock. The 2016 Parina earthquake did not rupture the full length of the late Quaternary scarps, implying that the Parina Fault does not slip in characteristic, repeat earthquakes. At Parina, and across most of the Peruvian Altiplano, normal faults are most-easily identified from recent scarps cutting late Quaternary moraine crests. In regions where there are no recently-deposited moraines, faults are difficult to identify and lack time constraints to quantify rates of fault slip. For this reason, current fault maps may underestimate the seismic hazard in the Altiplano. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Locating active faults in the Cusco Valley using magnetotelluric and radon gas data(Elsevier, 2025)This study presents a novel approach to identifying and characterizing active faults in urban areas, using an example from the city of Cusco in Peru, by combining magnetotelluric (MT) exploration and radon gas monitoring. The research aims to improve understanding of the active faults in the Cusco Valley by using the MT method to provide subsurface electrical resistivity data, enabling the mapping of fault structures and determination of fault properties. A 2-D inversion of the MT data resulted in resistivity models that revealed critical information about fault geometry, such as dip and depth. Radon gas measurements complement the MT data by being able to distinguish between active and inactive faults. This is because active faults can exhibit higher permeability due to ongoing tectonic activity. This increased permeability facilitates the migration of radon from deeper rock formations to the surface, leading to detectable anomalies. Active faults are particularly significant as their continued deformation enhances permeability, making radon anomalies a valuable indicator for locating these structures. A clear correlation was found between elevated radon concentrations (>5.9 kBq m−3) and the locations of faults identified through the MT resistivity model, and additional gas sample analyses ruled out the possibility that these anomalies were caused by lithological variations. This integrated approach holds significant potential for detecting active faults in urban areas such as Cusco. In these locations faults such as the Cusco and Alto Qosqo faults may be obscured by construction. The findings uncovered previously unmapped fault lineaments and advanced the understanding of fault kinematics in Cusco, emphasizing the importance of combining MT and radon monitoring for earthquake hazard assessment in urban environments.1