Browsing by Author "Benavente, Roberto"

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    A Consistently Processed Strong-Motion Database for Chilean Earthquakes
    (Seismological Society of America, 2022) Castro, Sebastián; Benavente, Roberto; Crempien de la Carrera, Jorge; Candia, Gabriel; Llera Martin, Juan Carlos de la
    © Seismological Society of America.Since the 1985 M 8.0 central Chile earthquake, national strong-motion seismic networks have recorded ten megathrust earthquakes with magnitudes greater than M 7.5 at the convergent margin, defined by the contact between the Nazca and South American plates. The analysis of these earthquake records have led to improved hazard analyses and design codes for conventional and seismically protected structures. Although strong-motion baseline correction is required for a meaningful interpretation of these records, correction methods have not been applied consistently in time. The inconsistencies between correction methods have been neglected in the practical use of these records in practice. Consequently, this work aims to provide a new strong-motion database for researchers and engineers, which has been processed by traceable and consistent data processing techniques. The record database comes from three uncorrected strong motion Chilean databases. All the records are corrected using a four-step novel methodology, which detects the P-wave arrival and introduces a baseline correction based on the reversible-jump Markov chain Monte Carlo method. The resulting strong motion database has more than 2000 events from 1985 to the date, and it is available to download at the Simulation Based Earthquake Risk and Resilience of Interdependent Systems and Networks (SIBER-RISK) project website.
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    A supervised machine learning approach for estimating plate interface locking: Application to Central Chile
    (2024) Barra, Sebastian; Moreno, Marcos; Ortega-Culaciati, Francisco; Benavente, Roberto; Araya, Rodolfo; Bedford, Jonathan; Calisto, Ignacia
    Estimating locking degree at faults is important for determining the spatial distribution of slip deficit at seismic gaps. Inverse methods of varying complexity are commonly used to estimate fault locking. Here we present an innovative approach to infer the degree of locking from surface GNSS velocities by means of supervised learning (SL) algorithms. We implemented six different SL regression methods and apply them in the Central Chile subduction. These methods were first trained on synthetic distributions of locking and then used to infer the locking from GNSS observations. We tested the performance of each algorithm and compared our results with a least squares inversion method. Our best results were obtained using the Ridge regression, which gives a root mean square error (RMSE) of 1.94 mm/yr compared to GNSS observations. The ML -based locking degree distribution is consistent with results from the EPIC Tikhonov regularized least squares inversion and previously published locking maps. Our study demonstrates the effectiveness of machine learning methods in estimating fault locking and slip, and provides flexible options for incorporating prior information to avoid slip instabilities based on the characteristics of the training set. Exploring uncertainties in the physical model during training could improve the robustness of locking estimates in future research efforts.
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    Conjunto de datos: SIBER-RISK Strong Motion Database
    (Datos de Investigación UC, ) Castro, Sebastián; Benavente, Roberto; Crempien de la Carrera, Jorge; Candia, Gabriel; Llera Martin, Juan Carlos de la
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    Effects of earthquake spatial slip correlation on variability of tsunami potential energy and intensities
    (2020) Crempien, Jorge G. F.; Urrutia, Alejandro; Benavente, Roberto; Cienfuegos, Rodrigo
    Variability characterization of tsunami generation is quintessential for proper hazard estimation. For this purpose we isolate the variability which stems solely from earthquake spatial source complexity, by simulating tsunami inundation in the near-field with a simplified digital elevation model, using nonlinear shallow water equations. For earthquake rupture, we prescribe slip to have a log-normal probability distribution function and von Karman correlation between each subfault pair, which we assume decreases with increasing euclidean distance between them. From the generated near-field inundation time-series, emanating from several thousand synthetic slip realizations across a magnitude 9 earthquake, we extract several tsunami intensity measures at the coast. Results show that all considered tsunami intensity measures and potential energy variability increase with increasing spatial slip correlations. Finally, we show that larger spatial slip correlations produce higher tsunami intensity measure exceedance probabilities within the near-field, which highlights the need to quantify the uncertainty of earthquake spatial slip correlation.
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    Relation Between Oceanic Plate Structure, Patterns of Interplate Locking and Microseismicity in the 1922 Atacama Seismic Gap
    (2023) Gonzalez-Vidal, Diego; Moreno, Marcos; Sippl, Christian; Baez, Juan Carlos; Ortega-Culaciati, Francisco; Lange, Dietrich; Tilmann, Frederik; Socquet, Anne; Bolte, Jan; Hormazabal, Joaquin; Langlais, Mickael; Morales-Yanez, Catalina; Melnick, Daniel; Benavente, Roberto; Muenchmeyer, Jannes; Araya, Rodolfo; Heit, Benjamin
    We deployed a dense geodetic and seismological network in the Atacama seismic gap in Chile. We derive a microseismicity catalog of >30,000 events, time series from 70 GNSS stations, and utilize a transdimensional Bayesian inversion to estimate interplate locking. We identify two highly locked regions of different sizes whose geometries appear to control seismicity patterns. Interface seismicity concentrates beneath the coastline, just downdip of the highest locking. A region with lower locking (27.5 & DEG;S-27.7 & DEG;S) coincides with higher seismicity levels, a high number of repeating earthquakes and events extending toward the trench. This area is situated where the Copiapo Ridge is subducted and has shown previous indications of both seismic and aseismic slip, including an earthquake sequence in 2020. While these findings suggest that the structure of the downgoing oceanic plate prescribes patterns of interplate locking and seismicity, we note that the Taltal Ridge further north lacks a similar signature.
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    What Can We Do to Forecast Tsunami Hazards in the Near Field Given Large Epistemic Uncertainty in Rapid Seismic Source Inversions?
    (2018) Cienfuegos Carrasco, Rodrigo Alberto; Catalan, Patricio A.; Urrutia, Alejandro; Benavente, Roberto; Aranguiz, Rafael; Gonzalez, Gabriel