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Item Restricted Analysis and Evaluation of Recent Deformation on the Huaytapallana Fault (Central Region of Peru) Based on Data Obtained from a Local Seismic Network(Seismological Society of America, 2024-11-14) Tavera, Hernando; Nina Figueroa, Vilma; Bernal Esquia, Yesenia Isabel; Mercado, ArturoIn the central region of Peru, two earthquakes with magnitudes of ==$M$==ₛ 5.6 and 6.2 occurred in 1969, originating from the Huaytapallana fault. As a result, two fault scarps formed on the surface: the first measuring 4 km and the second one 9.5 km in length, separated by a 4 km section without a surface scarp. A three‐year seismic campaign (2015–2018) conducted around the Huaytapallana fault has provided insights into its current dynamics. The 172 microearthquakes recorded, with magnitudes ranging from ==$M$==w 0.6 to 3.1, are distributed along the northeastern flank of the fault and extend over 40 km, including segments without visible surface scarps. The Huaytapallana fault is estimated to have a depth of around 15 km with a dip of 60° toward the northeast. The composite focal mechanisms indicate a deformation process due to compression, with a fault plane oriented in the north‐northwest–south‐southeast direction and dipping toward the northeast at angles between 55° and 60°. The ==$M$==w 4.7 earthquake in 2022 and its series of aftershocks exhibit a similar deformation pattern associated with the Huaytapallana fault. These results are consistent with the regional tectonics, which control the deformation processes in the Mantaro basin, originating from the convergence of the Nazca and South American plates. We consider that the significant microseismic activity occurring in areas without visible surface scarps suggests the accumulation of substantial deformation, which could lead to future earthquakes of greater magnitude that may cause significant surface displacements.Item Open Access Heterogeneous Locking and Earthquake Potential on the South Peru Megathrust From Dense GNSS Network(American Geophysical Union, 2024-01-30) Lovery, B.; Chlieh, M.; Norabuena Ortiz, Edmundo; Villegas Lanza, Juan Carlos; Radiguet, M.; Cotte, N.; Tsapong-Tsague, A.; Quiroz Sifuentes, Wendy; Sierra Farfán, C.; Simons, M.; Nocquet, J. M.; Tavera, Hernando; Socquet, A.The Central Andes subduction has been the theater of numerous large earthquakes since the beginning of the 21st Century, notably the 2001 Mw = 8.4 Arequipa, 2007 Mw = 8.0 Pisco and 2014 Mw = 8.1 Iquique earthquakes. We present an analysis of 47 permanent and 26 survey global navigation satellite system (GNSS) measurements acquired in Central-South Peru between 2007 and 2022 to better understand the frictional properties of the megathrust interface. Using a trajectory model that mimics the different phases of the cycle, we extract a coherent interseismic GNSS field at the scale of the Central Andes from Lima to Arica (12–18.5°S). Interseismic models on a 3D slab geometry indicate that the locking level is relatively high and concentrated between 20 and 40-km depth. Locking distributions indicate a high spatial variability of the coupling along the trench, with the presence of many locked patches that spatially correlate with the seismotectonic segmentation. Our study confirms the presence of a creeping segment where the Nazca Ridge is subducting; we also observe a lighter apparent decrease of coupling related to the Nazca Fracture Zone (NFZ). However, since the Nazca Ridge appears to behave as a strong barrier, the NFZ is less efficient to arrest seismic rupture propagation. Considering various uncertainty factors, we discuss the implication of our coupling estimates with size and timing of large megathrust earthquakes considering both deterministic and probabilistic approaches. We estimate that the South Peru segment could have a Mw = 8.4–9.0 earthquake potential depending principally on the considered seismic catalog and the seismic/aseismic slip ratio.Item Open Access Evaluación de la cinemática del deslizamiento de Cuenca en los Andes de Perú central mediante técnicas fotogramétricas y geodésicas(Universidad Politécnica de Valencia, 2024-07-29) Quiroz Sifuentes, Wendy; Villegas Lanza, Juan Carlos; Moroccoire, Keiko; Balladares, Oscar; Berduzco, MijaellLos deslizamientos de tierra representan un peligro importante en muchas regiones montañosas, incluidos los valles interandinos del Perú. En este estudio evaluamos la dinámica del deslizamiento de Cuenca, ubicado en Huancavelica en el centro de Perú, empleando fotogrametría y mediciones GNSS. Se ejecutaron mediciones interanuales en ocho zonas entre 2016 y 2023 para GNSS y dos campañas de levantamiento fotogramétrico en 2023 para comparar los cambios de la superficie en el tiempo. Los resultados mostraron desplazamientos del orden de los 3,7 a 11,7 cm con la técnica de nube de puntos y 2,7 a 15 cm con el análisis de los ortomosaicos, siendo concordantes entre sí. Los desplazamientos en los puntos donde se han realizado mediciones GNSS son similares en magnitud, sin embargo, difieren parcialmente en dirección. El estudio concluye que las técnicas fotogramétricas son aplicables para analizar la dinámica de deslizamientos.Item Open Access Comparison between rupture parameters of intermediate and deep earthquakes at the Peru Brazil–Bolivia border and northern Chile(Springer, 2024-07-09) Pro, Carmen; Tavera, Hernando; Mattesini, Maurizio; Escudero, Lucía; Buforn, Elisa; Udías, Agustín; Centeno, EstelaWe determined the main parameters of the source rupture process of intermediate- and deep-depth earthquakes occurring in the Peru–Brazil–Bolivia border region and northern Chile. The parameters of depth, fault-plane orientation, scalar seismic moment, slip distribution, and radiated seismic energy are obtained from seismograms. We selected 15 intermediate-depth earthquakes (100 km < h < 300 km) and 10 very deep earthquakes (h > 500 km) with magnitudes MW ≥ 6.0. For most events, the slip distribution over the rupture plane shows a single asperity, and the source time function presents a simple pulse. There are differences between intermediate-depth and deep earthquakes. The rupture areas, maximum slip and source time function (STF) duration are larger for intermediate-depth events than for deep events. Additionally, the STF’s show a sharper increase for deep earthquakes. The scaled radiated seismic energy shows larger values for deep depth events. The stress regime pattern derived from the obtained focal mechanism agrees with the geometry of the subduction of the Nazca plate. At intermediate depths, in the northern area up to 12°S, the stress pattern corresponds to a horizontal extension, while in the southern area, the tension axes dip at an angle of 30°. At deep depths, the stress regime corresponds to vertical compression in the north and dips of approximately 45° in the south.Item Open Access To Mix or Not to Mix: Details of Magma Storage, Recharge, and Remobilization during the Pacheco Stage at Misti Volcano, Peru (≤21–2 ka)(Oxford University Press, 2024-05-18) Takach, Marie K.; Tepley, Frank J.; Harpel, Christopher J.; Aguilar, Rigoberto; Rivera, MarcoWe investigate ten of the most recent tephra-fall deposits emplaced between ≤21 and 2 ka from the Pacheco stage of Misti volcano, Peru, to elucidate magma dynamics and explosive eruption triggers related to magma storage, recharge, and remobilization. Whole-rock, glass, and mineral textures and compositions indicate the presence of broadly felsic, intermediate, and mafic magmas in a chemically and thermally stratified magma storage system (Zones 1–3) that interact to differing extents prior to eruption. Intermediate magmas are defined by plagioclase + amphibole + two-pyroxenes + Fe-Ti oxides and phase equilibria indicate they formed at ~300 to 600 MPa and ~950°C to 1000°C. Intermediate magmas dominate the Pacheco stage and either erupted alone as hybridized magmas or mingled with minor volumes of cool felsic magmas (~800°C) in which only plagioclase + Fe-Ti oxides are stable. Felsic magmas do not exclusively comprise any tephra-fall deposit emplaced during the Pacheco stage but were remobilized by recharge and mixing with intermediate magmas in order to erupt. Furthermore, felsic-hosted amphibole cognate to the intermediate magmas are reacted despite the felsic magmas being water saturated, which suggests they are staged above the amphibole stability limit (≤200 MPa). The cryptic presence of mafic magmas is indicated by high-An plagioclase cores (An₇₄₋₈₈), rare anhedral olivine (Fo₇₇₋₈₀), and possibly high Mg# augite and amphibole (up to Mg# 84 and 77, respectively). The dearth of basalt to basaltic andesite melts recorded in erupted glasses and exclusivity of high-An plagioclase to crystal cores signals mafic magmas are staged deeper in the crust than the intermediate magmas. Periodic interactions between these magmas tracked via glass compositions and crystal exchange reveal an alternation between the production of mingled magmas and their eruption shortly after a recharge event, followed by a period of homogenization and eruption of hybridized magmas. As such, we identify magma recharge as a key mechanism by which half of the explosive eruptions were triggered in the Pacheco stage. A >100°C increase in Misti’s fumarole temperatures from 1967 to 2018 coincident with changes in fumarolic gas compositions is consistent with degassing of a mafic recharge magma, signaling that Misti could produce similar explosive eruptions in the future.Item Open Access Geological evidence of extensive N-fixation by volcanic lightning during very large explosive eruptions(National Academy of Sciences, 2024-02-05) Aroskay, Adeline; Martin, Erwan; Bekki, Slimane; Le Pennec, Jean-Luc; Savarino, Joël; Temel, Abidin; Manrique, Nelida; Aguilar, Rigoberto; Rivera, Marco; Guillou, Hervé; Balcone-Boissard, Hélène; Phelip, Océane; Szopa, SophieMost of the nitrogen (N) accessible for life is trapped in dinitrogen (N₂), the most stable atmospheric molecule. In order to be metabolized by living organisms, N₂ has to be converted into biologically assimilable forms, so-called fixed N. Nowadays, nearly all the N-fixation is achieved through biological and anthropogenic processes. However, in early prebiotic environments of the Earth, N-fixation must have occurred via natural abiotic processes. One of the most invoked processes is electrical discharges, including from thunderstorms and lightning associated with volcanic eruptions. Despite the frequent occurrence of volcanic lightning during explosive eruptions and convincing laboratory experimentation, no evidence of substantial N-fixation has been found in any geological archive. Here, we report on the discovery of a significant amount of nitrate in volcanic deposits from Neogene caldera-forming eruptions, which are well correlated with the concentrations of species directly emitted by volcanoes (sulfur, chlorine). The multi-isotopic composition (δ¹⁸O, Δ¹⁷O) of the nitrates reveals that they originate from the atmospheric oxidation of nitrogen oxides formed by volcanic lightning. According to these first geological volcanic nitrate archive, we estimate that, on average, about 60 Tg of N can be fixed during a large explosive event. Our findings hint at a unique role potentially played by subaerial explosive eruptions in supplying essential ingredients for the emergence of life on Earth.Item Open Access Earthquake Early Warning Starting From 3 s of Records on a Single Station With Machine Learning(American Geophysical Union, 2023-11-02) Lara, Pablo; Bletery, Quentin; Ampuero, Jean-Paul; Inza Callupe, Lamberto Adolfo; Tavera, HernandoWe introduce the Ensemble Earthquake Early Warning System (E3WS), a set of Machine Learning (ML) algorithms designed to detect, locate, and estimate the magnitude of an earthquake starting from 3 s of P-waves recorded by a single station. The system is made of six Ensemble ML algorithms trained on attributes computed from ground acceleration time series in the temporal, spectral, and cepstral domains. The training set comprises data sets from Peru, Chile, Japan, and the STEAD global data set. E3WS consists of three sequential stages: detection, P-phase picking, and source characterization. The latter involves magnitude, epicentral distance, depth, and back azimuth estimation. E3WS achieves an overall success rate in the discrimination between earthquakes and noise of 99.9%, with no false positive (noise mis-classified as earthquakes) and very few false negatives (earthquakes mis-classified as noise). All false negatives correspond to M ≤ 4.3 earthquakes, which are unlikely to cause any damage. For P-phase picking, the Mean Absolute Error is 0.14 s, small enough for earthquake early warning purposes. For source characterization, the E3WS estimates are virtually unbiased, have better accuracy for magnitude estimation than existing single-station algorithms, and slightly better accuracy for earthquake location. By updating estimates every second, the approach gives time-dependent magnitude estimates that follow the earthquake source time function. E3WS gives faster estimates than present alert systems relying on multiple stations, providing additional valuable seconds for potential protective actions.Item Restricted Petrological and geochemical constraints on the magmatic evolution at the Ampato-Sabancaya compound volcano (Peru)(Elsevier, 2023-09-23) Rivera, Marco; Samaniego, Pablo; Nauret, François; Mariño, Jersy; Liorzou, CélineIn order to gain insights into continental arc magmatic processes, we have conducted a petrological and geochemical study of major and trace elements and Sr, Nd, and Pb isotopes of the Ampato-Sabancaya compound volcano, which belongs to the Andean Central Volcanic Zone (CVZ). Whole-rock compositions for Ampato and Sabancaya range from andesites to dacites (56.7–69.3 wt% SiO2) and both belong to a medium- to high-K calk-alkaline magmatic series. Ampato-Sabancaya samples are characterized by high contents of large-ion lithophile elements (LILE; e.g., K, Rb, Ba, Th), low concentrations of high field strength elements (HFSE; e.g., Nb, Zr) and heavy rare earth elements (HREE; e.g., Yb), with consequently high La/Yb and Sr/Y ratios. An increase in these ratios is usually interpreted as a result of magmatic differentiation in the presence of garnet in the deep crust. A detailed analysis reveals that the rocks of Ampato-Sabancaya display three different compositional groups. (1) The first, composed mainly of andesites (56.7–59.8 wt% SiO2), corresponds to lavas from the early stage of the Ampato Basal edifice, as well as pyroclastic deposits from the Ampato Upper edifice. (2) The second group corresponds to andesitic and dacitic compositions (60.0–67.3 wt% SiO2) from the Ampato Basal edifice (Moldepampa stage), the Ampato Upper edifice, and the Sabancaya edifice. (3) The third group corresponds to dacitic compositions (65.0–69.3 wt% SiO2) associated with the Corinta Plinian fallout and pyroclastic flow deposits from the Ampato Upper edifice. This last group of dacites, erupted during the Ampato Upper edifice stage, have drastically different compositions from the other groups with Sr/Y (<27) and Sm/Yb (<4.7) ratios lower than other lavas and lacking evidence of amphibole and/or garnet fractionation during their genesis. As a whole, Sr, Nd, Pd isotopic ratios suggest that mantle-derived magmas are significantly affected by assimilation processes during their evolution, due to the thick (65–70 km) continental crust beneath the CVZ in southern Peru. In summary, the magmatic evolution of group 1 and 2 can be explained by a two-step model in which primitive magmas evolved in the deep crust in the so-called melting-assimilation-storage-homogenization (MASH)-type reservoirs by assimilation-fractional crystallization (AFC) processes involving garnet and/or amphibole. Then, amphibole-dominated upper crustal AFC processes and magma mixing are responsible for the geochemical diversity of the main ASCV trend. In contrats, the group 3 dacites followed an upper crustal AFC process (without amphibole) from a different primitive magma, which did not suffer the high pressure, garnet-dominated AFC processes. This evolution highlights the complexities associated to magma genesis and differentiation at continental arcs contructed on a thick crust.Item Open Access The late Pleistocene Sacarosa tephra-fall deposit, Misti Volcano, Arequipa, Peru: its magma, eruption, and implications for past and future activity(Springer, 2023-08-14) Harpel, Christopher J.; Cuno, Juan José; Takach, Marie K.; Rivera, Marco; Aguilar, Rigoberto; Tepley III, Frank J.; Garcia, FredyBetween 38.5 ka cal BP and 32.4 ka cal BP, a dacitic Volcanic Explosivity Index 5 eruption at Misti volcano emplaced the Sacarosa tephra-fall deposit. Its biotite phenocrysts, fine grain size, scarce lithics, and abundant loose crystals characterize the deposit at locations sampled. The eruption’s ~ 800 °C magma rose rapidly from ~ 10 km depth, culminating in a Plinian eruption which reached a mass eruption rate of 7.7 × 10⁶–4.1 × 10⁷ kg/s and emplaced about 3 km³ of tephra within tens of hours. The unit comprises two layers of subequal thickness separated by a diffuse contact with the upper distinguished by being slightly coarser and less well sorted than the lower. The deposit’s coarser upper layer indicates either climactic conditions or a lesser degree of fragmentation during the latter half of the eruption. Strong winds distributed the deposit southwest of Misti, where it crops out over at least 800 km² and drapes the present site of Arequipa with up to 100 cm of tephra. The Sacarosa deposit is the first among the Cayma stage deposits, a distinctive group of felsic, biotite-bearing units, to be carefully described and its eruption characterized. Several Cayma stage deposits were emplaced by voluminous explosive eruptions similar to the Sacarosa eruption, representing a ~ 8.9–15.5 ky interval of powerful eruptions. Such an explosive eruption today would threaten Arequipa’s over 1,100,000 residents, many of whom live within the Sacarosa deposit’s distribution.Item Open Access The 2013–2020 seismic activity at Sabancaya Volcano (Peru): Long lasting unrest and eruption(Elsevier, 2023-03) Machacca, Roger; Lesage, Philippe; Tavera, Hernando; Pesicek, Jeremy D.; Caudron, Corentin; Torres Aguilar, José Luis; Puma, Nino; Vargas, Katherine; Lazarte, Ivonne; Rivera, Marco; Burgisser, AlainSabancaya volcano is the youngest and second most active volcano in Peru. It is part of the Ampato-Sabancaya volcanic complex which sits to the south of the ancient Hualca Hualca volcano and several frequently active faults, thus resulting in complex volcano-tectonic interactions. After 15 years of repose, in 2013, a series of 4 earthquakes with magnitude >4.5 occurred within 24 h, marking the beginning of a new episode of unrest. Several additional swarms of earthquakes occurred in the following years until magmatic eruptive activity started on 6 November 2016. This activity is ongoing as of this writing, with an average of 50 explosions per day. In this study, we present results of multiparametric monitoring of Sabancaya's activity observed during 2013–2020. Seismic data are used to create a one-dimensional seismic velocity model, to catalog, locate, and characterize earthquakes, to detect repeating earthquake families, and to monitor seismic velocity variations by ambient noise cross-correlation. These analyses are complemented by visual and remote sensing observations and ground deformation measurements. All monitored parameters showed significant changes on 6 November 2016, the day of eruption onset, thus dividing the eruptive activity into pre-eruptive and eruptive stages...Item Open Access Volcanic risk management practice evolution between vulnerability and resilience: the case of Arequipa in Peru(Frontiers Media, 2022-09-29) Lièvre, Pascal; Mérour, Eléonore; Morin, Julie; Macedo Franco, Luisa Diomira; Ramos Palomino, Domingo; Rivera, Marco; Masías Alvarez, Pablo; van Wyk de Vries, BenjaminThis paper proposes a new way of understanding the debate between vulnerability and resilience. We mobilize on the theoretical level the notion of “paradigm” in the sense of Kuhn and, on the methodological level, Foucault’s notion of “apparatus” to understand volcanic risk management practices. Through an interdisciplinary approach, combining management, geography and Earth sciences, we study the evolution of volcanic risk management practice in Arequipa (Peru) from the 1990s to the present. To do this, we look at the history of volcanic risk management in Arequipa, using a qualitative interview methodology based on six in-depth centered interviews from the main actors of this history, supported by a 2-monthethnographywhichallowed access to large institutional documentation (reports, studies, archives, maps, pictures...). Management practices in Arequipa appear to be centered on the paradigm of vulnerability since the 1990s. Some operations since 2015 named as resilient emerge but they are still inscribed in the vulnerability paradigm. The results show the relevance of the theoretical and methodological framework chosen for Arequipa but also the possibility of using it in a more general way.Item Open Access Modeling tephra fall and sediment-water flows to assess their impacts on a vulnerable building stock in the city of Arequipa, Peru(Frontiers Media, 2022-05-17) Thouret, J.-C.; Arapa, Evelyn; Charbonnier, S.; Guerrero, A.; Kelfoun, K.; Cordoba, G.; Rodriguez, D.; Santoni, O.Arequipa, Peru’s second economic center hosting c. 1,110,000 inhabitants, is the largest South American city exposed to a large variety of natural hazards. At least 200,000 live in areas likely to be affected by hazards from El Misti volcano, located 17 km to the NE. A multidisciplinary project aims to address the impacts of tephra fall and frequent mass flows on the vulnerable building stock and roofs along two ravines that cross the city, enabling decision-makers to undertake retrofitting projects and improve urban risk planning. Two recent eruptions, that is, the 1440–1470 CE Vulcanian event and c. 2070 years BP Plinian eruption, were chosen as references for probable scenarios of potential tephra fall impacts from El Misti on the building roofs. Tephra fall impacts on the city depend on the eruptive style, column height, and patterns of wind directions and velocities over south Peru and roof mechanical resistance. Estimates of potential damage levels and cost range values rely on nine structural types and four classes of vulnerable roofs. Simulation runs of hyperconcentrated flows (HCF) and debris flows (DF), using three depth-averaged flow models (Titan2F, VolcFlow, and Flo-2D) along two drainage basins on the SW flank of El Misti and across Arequipa, examined three scenarios from a database of 39 recent events and other historical lahars. Simulation results showcase the extent toward the city, inundation depths ≤4.6 m, flow velocities ≤9 m/s, and dynamic pressure up to 100 kPa from three different magnitude HCFs and DFs. In both ravines, overbank flows occurred in key urban areas due to channel sinuosity and constrictions near bridges. Potential impacts on habitat stem from ranges of flow dynamic pressure and measurements of construction material. We estimated the monetary loss of buildings according to hyperconcentrated flows and debris flows scenarios to contribute to retrofitting procedure, implementation of defense work, and relocation policy.Item Restricted Ambient noise tomography of Misti volcano, Peru(Elsevier, 2022) Cabrera-Pérez, Iván; Centeno Quico, Riky; Soubestre, Jean; D'Auria, Luca; Rivera, Marco; Machacca, RogerTo better understand the recent internal structure of Misti volcano, we determined a 3D S-wave velocity model applying Ambient Noise Tomography (ANT). We used data from 23 broadband and short-period seismic stations temporarily installed at Misti volcano between March and December 2011. This dataset allowed us to obtain empirical Green's functions by cross-correlating seismic ambient noise signals. Then, we retrieved 104 dispersion curves using the frequency-time analysis (FTAN) and, through a non-linear multiscale inversion, we obtained nine 2-D Rayleigh waves group velocity maps for periods in the range 0.7 s - 2 s. Finally, we carried out the depth inversion through a Bayesian transdimensional inversion to obtain a 3-D S-wave velocity model down to 3 km depth. Our study highlights five relevant seismic velocity anomalies. We observed the presence of three high-velocity zones located in the west-northwest, southwest and southeast parts of the crater, that could be related to intrusive bodies possibly associated with the formation of Misti volcano. We also observed two low-velocity anomalies in the volcano's western and central parts, which coincide with previous studies' findings and are related to fractured and weakened materials associated with the external caldera collapse and recent eruption episodes.Item Open Access Estimación de desplazamientos ocasionados por deslizamientos de tierra en la ciudad de Huancabamba, Piura, mediante análisis de imágenes satelitales para el periodo 2017-2019(Universidad Nacional Mayor de San Marcos, 2021-12-16) Alayo, Joel; Villegas Lanza, Juan CarlosEn este estudio se ha estimado y analizado los desplazamientos producidos por remociones en masa en la ciudad de Huancabamba y sus alrededores, aplicando procesos de correlación subpíxel, basado en transformadas de Fourier, a imágenes ópticas satelitales (SPOT 6 y Sentinel 2) para el periodo 2017-2019. Los resultados han permitido identificar 14 zonas de mayor deformación superficial, distribuidas en toda el área de estudio. Once de estas zonas comprenden magnitudes de desplazamientos entre 0.17 m a 0.83 m, con velocidades de propagación entre 0.2x10⁻⁵ mm/s y 2.8x10⁻⁵ mm/s. Mientras que 3 zonas específicas dentro de la ciudad, presentan tasas de desplazamiento lento pero continuo con magnitudes de 0.10 m hasta 0.25 m y con velocidades 1.6x10⁻⁶ mm/s y 4.9x10⁻⁶ mm/s. Para validar y correlacionar los resultados, se analizan desplazamientos GPS medidos en una red de puntos geodésicos y se correlacionan aspectos morfodinámicos; asimismo se evalúa la ocurrencia de sismicidad local y regional y niveles de precipitación como posibles detonantes. Esta investigación ha permitido generar información técnica de base sobre la identificación de zonas de peligro en la ciudad de Huancabamba y alrededores, que sirve de insumo para la caracterización de las zonas inestables y propensas a deslizamientos de tierra, de esta manera, aportando a la gestión de riesgo de desastres en dicha localidad.Item Restricted Bayesian parameter estimation for space and time interacting earthquake rupture model using historical and physics-based simulated earthquake catalogs(Seismological Society of America, 2021-12) Ceferino, Luis; Galvez, Percy; Ampuero, Jean‐Paul; Kiremidjian, Anne; Deierlein, Gregory; Villegas Lanza, Juan CarlosThis article introduces a framework to supplement short historical catalogs with synthetic catalogs and determine large earthquakes’ recurrence. For this assessment, we developed a parameter estimation technique for a probabilistic earthquake occurrence model that captures time and space interactions between large mainshocks. The technique is based on a two‐step Bayesian update that uses a synthetic catalog from physics‐based simulations for initial parameter estimation and then the historical catalog for further calibration, fully characterizing parameter uncertainty. The article also provides a formulation to combine multiple synthetic catalogs according to their likelihood of representing empirical earthquake stress drops and Global Positioning System‐inferred interseismic coupling. We applied this technique to analyze large‐magnitude earthquakes’ recurrence along 650 km of the subduction fault’s interface located offshore Lima, Peru. We built nine 2000 yr long synthetic catalogs using quasi‐dynamic earthquake cycle simulations based on the rate‐and‐state friction law to supplement the 450 yr long historical catalog. When the synthetic catalogs are combined with the historical catalog without propagating their uncertainty, we found average relative reductions larger than 90% in the recurrence parameters’ uncertainty. When we propagated the physics‐based simulations’ uncertainty to the posterior, the reductions in uncertainty decreased to 60%–70%. In two Bayesian assessments, we then show that using synthetic catalogs results in higher parameter uncertainty reductions than using only the historical catalog (69% vs. 60% and 83% vs. 80%), demonstrating that synthetic catalogs can be effectively combined with historical data, especially in tectonic regions with short historical catalogs. Finally, we show the implications of these results for time‐dependent seismic hazard.Item Restricted Advances in scientific understanding of the Central Volcanic Zone of the Andes: a review of contributing factors(Springer, 2022-02-12) Aguilera, Felipe; Apaza, Fredy; Del Carpio Calienes, José Alberto; Grosse, Pablo; Jiménez, Néstor; Ureta, Gabriel; Inostroza, Manuel; Báez, Walter; Layana, Susana; Gonzalez, Cristóbal; Rivera, Marco; Ortega, Mayra; Gonzalez, Rodrigo; Iriarte, RodrigoThe Central Volcanic Zone of the Andes (CVZA) has been the focus of volcanological research for decades, becoming a very important site to understand a number of volcanic processes. Despite most of the research in the CVZA being carried out by foreign scientists, the last two decades have seen a significant increase in contributions by regional researchers. This surge has been facilitated by the creation of new volcanic observatories, improvement of the monitoring networks, creation of postgraduate programs where new local volcanologists are trained, creation of specialized research nuclei or groups, and increasing investment in research. This article presents a review of the evolution of the contributions of the regional volcanological community to the knowledge of the CVZA in the last 20 years (2000–2019), both from research and monitoring institutions in Peru, Bolivia, Argentina, and Chile. Based on updates made by the regional groups, a new list of active/potentially active volcanoes of the CVZA is presented, as is a complete database for article published on the CVZA. We find that a significant motivator has been regional volcanic unrest that has triggered new investment. Perú is the country with the highest investment in monitoring and research and is the best instrumented, Argentina is the country with the highest number of local participation in published papers in the domain of volcanology and magmatic systems, and Chilean volcanoes are the focus of the highest number of articles published. The current situation and general projections for the next decade (2020–2030) are also presented for each country, where we believe that the over the next 10 years, will be increased the monitoring and research capabilities, improved the scientific knowledge with more participation of regional institutions, and strengthen the collaboration and integrated work between CVZA countries, especially in border volcanoes.Item Restricted Multidisciplinary study of the impacts of the 1600 CE Huaynaputina eruption and a project for geosites and geo-touristic attractions(Springer, 2021-07) Mariño, Jersy; Cueva, Kevin; Thouret, Jean-Claude; Arias, Carla; Finizola, Antony; Antoine, Raphael; Delcher, Eric; Fauchard, Cyrille; Donnadieu, Franck; Labazuy, Philippe; Japura, Saida; Gusset, Rachel; Sanchez, Paola; Ramos, Domingo; Macedo Franco, Luisa Diomira; Lazarte, Ivonne; Liliane, Thouret; Del Carpio Calienes, José Alberto; Jaime, Lourdes; Saintenoy, ThibaultThe Huaynaputina volcano, southern Peru, was the site of the largest historical eruption (VEI 6) in the Andes in 1600 CE, which occurred during the historic transition between the Inca Empire and the Viceroyalty of Peru. This event had severe consequences in the Central Andes and a global climatic impact. Spanish chronicles reported that at least 15 villages or settlements existed around the volcano, of which seven of them were totally destroyed by the eruption. Multidisciplinary studies have allowed us to identify and analyze the characteristics of six settlements buried by the eruption. Tephra fallout and pyroclastic current deposits (PDCs) had different impacts according to the settlement distance from the crater, the location with respect to the emplacement of PDCs along valleys, the geomorphological characteristics of the site, and type of constructions. Thus, Calicanto, Cojraque, and San Juan de Dios, located beneath the main axis of tephra dispersal lobe due west and/or on valley edges, were buried under several meters of pyroclastic deposits, while the villages of Estagagache, Chimpapampa, and Moro Moro, located to the S and SE of the lobe, were partially mantled by tephra. The 1600 CE Huaynaputina eruption created an important geological and cultural heritage, which has scientific, educational, and touristic values. Geo-touristic attractions are proposed based on identification, characterization, and qualitative evaluation of four groups totaling 17 geosites: volcanic geosites, volcanic-cultural geomorphosites, and hot springs. Seven geological roads along with seven viewpoints are proposed, which allow to value the most relevant landscapes, deposits and geological structures.Item Restricted Probing the hidden magmatic evolution of El Misti volcano (Peru) with the Pb isotope composition of fumaroles(Springer, 2022-01-20) Vlastelic, Ivan; Apaza, Fredy; Masias, Pablo; Rivera, Marco; Piro, Jean‐Luc; Gannoun, AbdelmouhcineThis work proposes a new method to probe the hidden magmatic evolution of quiescent Andean volcanoes from the Pb isotope composition of gases. The method is based on an assimilation-fractional crystallisation-degassing model linking the Pb isotope composition of gases with the SiO₂ content of their magmatic source. The model is applied to El Misti volcano that threatens Arequipa, the second most densely populated city of Peru. Gas condensates and Pb-rich solid deposits (PbS, PbCl₂, PbSO₄) collected in 2018 in the bottom of El Misti crater at 260–150°C fumarole vents were used to reconstruct the mean composition of degassing magmas (60.8-61.8 wt% SiO₂). These compositions are slightly more evolved than the lavas from the last AD 1440–1470 eruption, suggesting either the secular differentiation of the main magma reservoir, or the contribution of more evolved magmas to volcanic gases. On the other hand, the slight but significant difference between the instantaneous composition recorded in gas condensates and the time-integrated composition recorded in solid deposits points to the degassing of less evolved magmas over the last decades. This trend is ascribed to a recent recharge of El Misti reservoir with hot mafic magmas, in agreement with the evolution of fumarolic deposit mineralogy in the last half a century. The Pb isotope composition of gas appears to be a promising tool for probing the hidden magmatic evolution of quiescent volcanoes where assimilation-fractional crystallisation operates.Item Open Access Monitoreo de volcanes activos en Perú por el Instituto Geofísico del Perú: Sistemas de alerta temprana, comunicación y difusión de la información(Volcanica, 2021-11-01) Machacca, Roger; Del Carpio Calienes, José Alberto; Rivera, Marco; Tavera, Hernando; Macedo Franco, Luisa Diomira; Concha Calle, Jorge Andrés; Lazarte Zerpa, lvonne Alejandra; Centeno Quico, Riky; Puma Sacsi, Nino; Torres, José; Vargas Alva, Katherine Andrea; Cruz Igme, John Edward; Velarde Quispe, Lizbeth; Vilca, Javier; Malpartida, AlanEl monitoreo volcánico en Perú es realizado por el Instituto Geofísico del Perú (IGP), a través de su Centro Vulcanológico Nacional (CENVUL). El CENVUL monitorea 12 de los 16 volcanes considerados como activos y potencial-mente activos, localizados en el sur del Perú y emite boletines periódicos sobre la actividad volcánica, y dependiendo del nivel de alerta de cada volcán también emite alertas vulcanológicas de dispersión de ceniza y ocurrencia de lahares. La información generada por el CENVUL se difunde a las autoridades civiles y al público en general a través de diferentes medios de comunicación (boletines, correo electrónico, web, redes sociales, aplicativo móvil, etc.). El grupo de vulcanología del IGP se formó después de la erupción del volcán Sabancaya en 1988. Desde entonces, los estudios geofísicos y geológicos, la evaluación de peligros volcánicos y el monitoreo multidisciplinario realizado por el IGP, han permitido conocer en profundidad la actividad volcánica pasada y reciente ocurrida en Perú, para prever futuros escenarios eruptivos. Actualmente, el 80 % de los volcanes activos y potencialmente activos del Perú están equipados con redes de instrumentos multiparamétricos, siendo el monitoreo sísmico el más extendido. En este artículo, presentamos la situación actual del monitoreo volcánico en el Perú, las redes de monitoreo y las técnicas empleadas, así como los esfuerzos de educación e información al público y a las autoridades responsables del manejo de riesgo de desastres.Item Open Access Monitoring of active volcanoes in Peru by the Instituto Geofísico del Perú: Early warning systems, communication, and information dissemination(Volcanica, 2021-11-01) Machacca, Roger; Del Carpio Calienes, José Alberto; Rivera, Marco; Tavera, Hernando; Macedo Franco, Luisa Diomira; Concha Calle, Jorge Andrés; Lazarte Zerpa, lvonne Alejandra; Centeno Quico, Riky; Puma Sacsi, Nino; Torres, José; Vargas Alva, Katherine Andrea; Cruz Igme, John Edward; Velarde Quispe, Lizbeth; Vilca, Javier; Malpartida, AlanVolcano monitoring in Peru is carried out by the Instituto Geofísico del Perú (IGP), through its Centro Vulcanológico Nacional (CENVUL). CENVUL monitors 12 out of 16 volcanoes considered as historically active and potentially active in southern Peru and issues periodic bulletins about the volcanic activity and, depending on the alert-level of each volcano, also issues alerts and warnings of volcanic unrest, ash dispersion, and the occurrence of lahars. The information generated by CENVUL is disseminated to the civil authorities and the public through different information media (newsletters, e-mail, website, social media, mobile app, etc.). The IGP volcanology team was formed after the eruption of Sabancaya volcano in 1988. Since then, geophysical and geological studies, volcanic hazards assessments, and multidisciplinary monitoring realized by the IGP, have provided a comprehensive understanding of volcanic activity in Peru and forecast future eruptive scenarios. Currently, 80% of the historically active and potentially active volcanoes in Peru are equipped with networks of multiparameter instruments, with the seismic monitoring being the most widely implemented. In this report, we present the situation of volcanic monitoring in Peru, the monitoring networks, the techniques employed, as well as efforts to educate and inform the public and officials responsible for disaster risk management.