César Pastén

Empirical Site Classification of CSN Network Using Strong‐Motion Records

The National Seismological Center of the University of Chile (CSN, Centro Sismologico Nacional) has been operating more than 400 seismic stations throughout the country. The data collected from this network, from March 2012 to August 2017, includes more than 4000 Chilean strong‐motion records, from more than 1000 events (magnitudes ranging from 4.0 up to 8.3). In this study, we use this data set and classify 118 stations from this network, using the horizontal‐to‐vertical response spectral ratio (HVRSR) of strong‐motion records. This classification considers not only the predominant period obtained from the average HVRSR but also the peak amplitude from this curve. The results indicate no correlation between the two parameters, despite the common practice of combining all curves with similar predominant periods. Even more, we believe that relevant information of the site’s impedance contrast between the soil and bedrock is lost in the process of averaging HVRSR curves from different stations.

Geophysical Characterization of the Chilean Seismological Stations: First Results

The Chilean Seismological Network has been rapidly growing in recent years, going from a few dozens stations working before 2010 to nearly a 100 installed all over the territory. Even more, nearly 300 strong-motion stations from the Accelerographic National Network have recently complemented this network, mainly deployed in large cities, at a variety of site conditions. All of these stations are currently providing useful information of Chilean earthquakes and are expected to record moderate-to-large events. However, the lack of appropriate site characterization sets an important limit to its usefulness. In this work, we present the geophysical characterization of 163 stations, the first results of larger effort to complete the characterization at all sites, based on array measurements of microtremors and horizontal-to-vertical spectral ratios. This information will help improve our understanding of the dynamic behavior of soils during earthquakes, providing relevant information for seismic design and seismic codes. Electronic Supplement: Figures showing distribution of the geophones, and table with nearly 400 seismic stations managed by the Centro Sismológico Nacional of Universidad de Chile (CSN), along with their location and, the average S-wave velocity in the upper 30 m and the horizontal-to-vertical spectral ratio.

Numerical study on long-term monopile foundation response

ABSTRACT This paper analyzes the long-term monopile foundation that undergoes numerous mechanical cycles. The semiempirical scheme is adopted to involve a mechanical constitutive model to extract stress and strains at the first cycle and polynomial-type strain accumulation functions to track the progressive plastic deformation. In particular, the strain function contains the fundamental features that require simulating the long-term response of geomaterials: volumetric strain (terminal void ratio) and shear strain (shakedown or ratcheting), the strain accumulation rate, and stress obliquity. The numerical simulation shows evolution of displacements, pile rotation, and stress redistribution along the embedded pile as the number of load cycles increases. The analysis highlights that the pile rigidity affects the pattern of horizontal stress and displacement. The repetitive lateral load enhances the lateral load resistance due to soil densification along the pile.

The Impact of a Buried High‐Velocity Layer in the Seismic Site Amplification of the City of Llolleo, ChileThe Impact of a Buried HVL in the Seismic Site Amplification of the City of Llolleo, Chile

Programa de Riesgo Sismico (PRS) at the University of Chile Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) 2017-21171480 Fondo Nacional de Desarrollo Cientifico y Tecnologico (FONDECYT) 1170430 Advanced Mining Technology Center AMTC FB0809 PIA CONICYT

Estudio de efectos de sitio en la Región de Coquimbo durante el terremoto de Illapel Mw 8.3 de 2015

1 Departamento de Ingeniería Civil, Universidad de Chile, Av. Blanco Encalada 2002, Santiago, Chile, jose.fernandez@ing.uchile.cl, cpasten@ing.uchile.cl 2 Departamento de Geofísica, Universidad de Chile, Av. Blanco Encalada 2002, Santiago, Chile, sruiz@dgf.uchile.cl 3 Centro Sismológico Nacional, Universidad de Chile, Av. Beaucheff 1225, Santiago, Chile, leyton@csn.uchile.cl Study of site effects in the Coquimbo Region due to the 2015 Mw 8.3 Illapel, Chile, Earthquake