Browsing by Author "Calisto, Ignacia"

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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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    Characterization of historical megathrust earthquake ruptures in Central Chile using logic tree analysis
    (2024) San Martin, Javiera; Calisto, Ignacia; Quezada, Jorge; Stewart, Daniel; Ely, Lisa; Cifuentes-Lobos, Rodrigo; Moreno, Marcos
    Characterizing the spatial distribution of ruptures from historical and recent earthquakes is key to understanding the seismic cycle of large earthquakes in subduction zones, and thus to assessing the potential risks associated with future earthquakes. Central Chile (35 degrees S38 degrees S) has been repeatedly affected by large earthquakes, such as the 2010 Maule (Mw 8.8) and the 1835 earthquakes witnessed by Robert Fitzroy (HMS Beagle captain). Here, we identify the rupture pattern and tsunami propagation of the 1751, 1835, and 2010 mega-earthquakes, events that overlapped in central Chile, by compiling historical records and applying robust statistical tools. We used an adaptation of a logic tree methodology to generate random sources of slip distribution for each event, constrained by tsunami and vertical deformation data. We find that the three events studied have different slip peaks. The 1751 earthquake has the largest slip with a maximum patch of similar to 26 m, while the 2010 and 1835 earthquakes reach slips of similar to 16 m and similar to 10 m, respectively. Our results show that a part of the margin between 36 degrees S and 37 degrees S was consistently affected by large earthquakes, but with different slip and depth. The shallower depths of the megathrust north of 36 degrees S accumulated energy for at least 300 years, which was released by the 2010 earthquake. Our results provide important constraint for rupture patterns and spatial relationships between historical and recent earthquakes, thus extending the time scale for seismic slip distribution analyses over multiple cycles and contributing to a more comprehensive understanding of seismic hazards.