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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, Pliocene river capture and incision of the northern altiplano: Machu Picchu, Peru(Geological Society of London, 2020-01-01)The Abancay Deflection, forming the northern edge of the Altiplano in the Peruvian Andes, is a remarkable geomorphological feature marking the along-strike segmentation of the Andes. Little is known about the timing and spatial distribution of exhumation in this area. To constrain the exhumation history of the Abancay Deflection and its drivers, we present apatite (U–Th)/He and fission-track thermochronology data from samples collected along an elevation transect at Machu Picchu. Geomorphological analysis demonstrates recent and continuing drainage reorganization recorded by the spatial distribution of the normalized steepness index ( k sn ) and normalized integrated drainage area ( χ ) parameters. Thermochronologically derived cooling rates are converted into exhumation using regionally constrained geothermal gradients between 16 and 26°C km −1 . Time–temperature inversions imply steady and slow exhumation (<0.05 km Ma −1 ) between 20 and 4 Ma, followed by rapid exhumation (>0.9 km Ma −1 ) since 4 Ma. The timing of rapid exhumation, combined with the geomorphological analysis, suggests that fluvial capture of the previously endorheic Altiplano by the Urubamba River drove recent incision and exhumation. Depending on the value of the geothermal gradient used, total exhumation since 4 Ma can be explained by river incision alone or requires additional exhumation driven by tectonics, possibly associated with movement on the Apurimac fault. Supplementary material: Additional information is available at 10.6084/m9.figshare.c.5177343 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Inventory of large landslides along the Central Western Andes (ca. 15°–20° S): Landslide distribution patterns and insights on controlling factors(Elsevier Ltd, 2022-06-01)The western flank of the Central Andes hosts some of the largest terrestrial landslides (v > km3), which morphologies are particularly well-preserved due to low erosion rates related to the hyper-arid climate prevailing in this region since the Miocene. First-order questions are pending about the factors controlling the development and the triggering of those large-scale slope failures. Previous studies provided some geomorphological analysis and dating on individual study cases, but a regional-scale vision of landslide processes long the Central Western Andes is missing. Here we report an original inventory of large landslides (areas from 0.1 to 180 km2) established along the western flank of the Central Andes between latitudes ca. 15 and 20° S, and from the Pacific coast to the Altiplano. Based on manual mapping (using satellite images analysis, Google Earth and DEMs analysis) and a compilation of previous works, we inventoried more than a thousand large landslides in this region. We then statistically explored the database according to the landslides typology, size, abundance and relation to geologic, tectonic and climatic settings of the Central Western Andes in order to provide a first insight on their controlling factors. Landslide size-frequency distribution follows a power-law with an exponent of 2.31 ± 0.16 and a cut-off of 4.0 ± 1.9 km2 showing a strong contribution of the largest landslides to the cumulated landslide area. We revealed a dominance of rockslide typology (86%) characterized by in-mass slides, the rest being rock-avalanche type (14%) marked by typical granular-flow morphologies. Combination of specific lithology and great local relief emerge as favorable conditioning factor for large landslide initiation, in particular in the case of river incisions though ignimbrites of the Paleogene-Neogene (Huaylillas Formation), concentrating >30% of the landslides. Moreover, landslide clusters tend to follow crustal faults networks suggesting a long-term control of tectonic activity. Most of the identified landslides are paleo events. We tentatively argue that their triggering could not have been possible in the current hyper-arid conditions of the Atacama Desert and its periphery. Future research providing dating on some of the landslide clusters identified in this study is needed to explore possible temporal correlations between periods of landslide activity and external seismic and/or climatic cycles. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Paleoseismic evidence of the 1715 C.E. earthquake on the Purgatorio Fault in Southern Peru: implications for seismic hazard in subduction zones(Elsevier B.V., 2022-07-05)Active faults in the forearc of southern Peru pose a poorly understood hazard to the region. The Purgatorio Fault is a 60 km-long fault that extends between Moquegua and Tacna that has hosted several scarp-forming earthquakes over the last 6 ka. We present new measurements of the fault scarp geomorphology along the Purgatorio Fault, and use dating of the stratigraphy within a new paleoseismic trench excavated across the fault to establish the chronology of scarp formation. We find that the most recent surface-rupturing earthquake on the Purgatorio Fault occurred sometime between 1630C.E and 1790C.E and had a moment magnitude (Mw) of ~7. We propose that this most recent surface-rupturing earthquake on the Purgatorio Fault was the 1715C.E earthquake recorded in the historical catalogue of the region, which was previously attributed to the megathrust offshore. Our results highlight the importance of establishing a paleoseismic record of onshore faults to differentiate between major megathrust and forearc earthquakes. Given the proximity of these shallow, onshore faults to coastal communities in Peru, the shallow earthquakes they generate may pose a severe, yet often overlooked, seismic hazard. - 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(RELX Group (Netherlands), 2024-01-01) - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Baseline radon concentrations in uranium-rich and faulted zones of the Eastern Cordillera, Central Andes, Peru(Elsevier BV, 2026-08-01)Radon is a naturally occurring radioactive gas that poses environmental and health concerns, particularly in regions characterized by uranium-rich geological formations and active fault systems that facilitate its migration from the subsurface into soil gas and near-surface environments. In the Eastern Cordillera of the Central Andes, southern Peru, uranium-bearing deposits intersected by geological faults create favorable conditions for elevated radon concentrations in the soil gas and near-surface environment, due to increased permeability that enhances upward transport. However, lack of systematic data on radon concentrations in these areas has limited development of a national radon framework and constrained regional assessments. This study establishes baseline concentrations of soil gas radon (Rn-222) in faulted and uranium-bearing zones of the Eastern Cordillera. Sixteen measurement sites were surveyed across key geological units, integrating lithogeochemical analyses of uranium in rock samples with in-situ radon measurements. Results reveal spatial variability, with soil gas radon concentrations reaching up to 567 kBq/m3, including high values in structurally controlled zones despite relatively low uranium content (23 ppm). These findings demonstrate that, while uranium-rich lithologies act as primary radon sources, fault-controlled permeability and fracture networks exert dominant control on radon migration. By integrating geological, geochemical, and radon data, this study provides a framework for radon mapping in Peru. Results highlight role of structural geology in radon distribution and support soil gas radon as indicator of uranium mineralization and fault-related permeability. These insights contribute to improved radon assessment strategies and provide scientific basis for future development of a national radon potential map.