Papers by Cristian Otarola
Stochastic strong-ground motion simulation in the Santiago metropolitan region considering an Mw 7.8 intraplate intermediate-depth earthquake
Journal of South American Earth Sciences
Stochastic strong motion generation using slip model of 21 and 22 May 1960 mega-thrust earthquakes in the main cities of Central-South Chile
High frequency sources controls strong motion of Mw 8.8 Maule 2010 earthquake
Bulletin of the Seismological Society of America, 2018
The 2011 Tohoku-Oki megathrust earthquake and its aftershocks were well recorded by the KiK-net n... more The 2011 Tohoku-Oki megathrust earthquake and its aftershocks were well recorded by the KiK-net network in accelerographs placed inside boreholes and on the surface. These data allow comparing strong-motion records with synthetic acceleration time histories for this large magnitude earthquake that caused extensive damage in Japan. Generating synthetic accelerograms at high frequencies can be approached using different techniques. We use the stochastic method to simulate horizontal and vertical strong-motion accelerograms in hard-rock boreholes; additionally, we incorporate P, SV, and SH soil amplification transfer functions to generate surface accelerograms. We reproduce the three components of the strong motion for 18 stations of the M w 9.0 mainshock event; additionally, we simulated 8 stations for an M w 6.9 aftershock. Our simulated acceleration time histories show similarity in time and frequency with the acceleration records for the period band between 0.05 and 1 s. Electronic Supplement: Table of the velocity model used in the modeling of our synthetic records, and figures showing comparison of time series and 5% response spectra of synthetic and real data of 2011 Tohoku-Oki megathrust earthquake and an M w 6.9 aftershock. BSSA Early Edition / 1
Geophysical Research Letters, 2017
The Valparaiso 2017 sequence occurred in the Central Chile megathrust, an active zone where the l... more The Valparaiso 2017 sequence occurred in the Central Chile megathrust, an active zone where the last mega-earthquake occurred in 1730. Intense seismicity started 2 days before the M w 6.9 mainshock, a slow trenchward movement was observed in the coastal GPS antennas and was accompanied by foreshocks and repeater-type seismicity. To characterize the rupture process of the mainshock, we perform a dynamic inversion using the strong-motion records and an elliptical patch approach. We suggest that a slow slip event preceded and triggered the M w 6.9 earthquake, which ruptured an elliptical asperity (semiaxis of 10 km and 5 km, with a subshear rupture, stress drop of 11.71 MPa, yield stress of 17.21 MPa, slip weakening of 0.65 m, and kappa value of 1.98). This earthquake could be the beginning of a long-term nucleation phase to a major rupture, within the highly coupled Central Chile zone where a megathrust earthquake like 1730 is expected.
Bulletin of the Seismological Society of America, 2016
The generation of accelerograms using stochastic methods has been a very useful methodology for s... more The generation of accelerograms using stochastic methods has been a very useful methodology for solving the problem of the lack of appropriate strongmotion records for seismic design. Here, we propose the generation of synthetic strong motion for subduction earthquakes that present well-developed P waves and energetic arrivals of S waves associated with the main asperities of the source of these events. The first few seconds of these accelerograms are dominated by P waves; however, the strong motion is a mixture of S and P waves arriving at the same time. The traditional method considers only S waves. We propose to improve the stochastic generation of accelerograms taking into account a stratified velocity model, incident and azimuthal angles, free surface factors, and energy partition to incorporate the P and SV waves in the simulation. Finally, the simulated accelerograms are compared with the observed data recorded on rock by the Integrated Plate boundary Observatory Chile (IPOC) network during the 2007 Tocopilla and 2014 Iquique earthquakes. The use of P, SV, and SH waves in the stochastic simulation allowed us to generate three-component synthetic records. The early seconds are clearly associated with P waves, and the three components reproduce the shape and the amplitude in time and spectral domains for the observed and simulated records. Online Material: Figures showing fit between observed and simulated waveforms, maximum amplitude of acceleration response spectra, peak ground velocities, and peak ground accelerations. BSSA Early Edition / 1
Dynamic rupture of subduction earthquakes located near the trench
Earth and Planetary Science Letters
Abstract We perform kinematic and dynamic source inversions of four interplate thrust earthquakes... more Abstract We perform kinematic and dynamic source inversions of four interplate thrust earthquakes that occurred near the trench at the base of the continental wedge in Northern Chile and we compare them to deeper intraplate events. The magnitudes of these interplate events were between Mw 6.3 and Mw 6.5, with hypocentral depths varying between 17.8 km and 28 km. These earthquakes correspond to one foreshock and three aftershocks of the large 2014 Mw 8.2 Iquique earthquake. The geometry of the seismic rupture obtained from the kinematic and dynamic inversions were similar for the four earthquakes studied and their dynamic source parameters are in accordance with typical interplate earthquakes around Mw 6.5. We compare the dynamic rupture of these events with those of five intraplate, intermediate-depth earthquakes that occurred in Northern Chile, Japan, Argentina and Mexico with depths between 57 km and 250 km. We also compare these events with the Mw 6.9 Valparaiso earthquake that was also a shallow interplate thrust event. Results show that the main dynamic parameters of the interplate events (stress in the nucleation zone, overall stress drop and fracture energy rate) were smaller than those of the intraplate intermediate-depth earthquakes. Furthermore, we compare our results with those obtained with several methodologies commonly used to estimate values of stress drop, fault radius and corner frequency. We find some minor differences between them for most of the earthquakes analyzed. Finally, we infer from our results that the studied area, located in the subduction interface zone near the trench, is suitable for earthquake nucleation of small to moderate earthquakes and does not represent a barrier for a future large tsunamigenic rupture.
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Papers by Cristian Otarola