Effects of local site, propagation path and source in ground motion records observed in Lima, Peru, were separated by the spectral inversion method proposed by Iwata and Irikura (1986 [1], 1988 [2]) to examine the relation between local subsurface conditions and local site amplifications in a frequency range from 0.5 to 20 Hz. S-wave portions of accelerograms in horizontal components observed at 5 stations for 11 events along the Pacific coast of Lima city, Peru, were analyzed. The Q factor was obtained from our inversion results as frequency dependent function QS( f) = 80.4 f 0.63. In terms of local site effects, stations located on alluvial gravel deposits were likely to suffer amplification at frequencies larger than 4 Hz, while one station (CAL site) located on soft soil sediment has different behavior of amplification. We also compared our results with 1-D theoretical computation, o...

El 1 de octubre de 2005, ocurrió un sismo de magnitud moderada (5.4 ML) en la región Sur de Perú afectando a un área que involucra diversas localidades situadas alrededor del volcán Ticsani. El epicentro del sismo fue ubicado a 8 km al Este de la localidad de Calacoa y 62 km al NE de la ciudad de Moquegua. El sismo produjo daños en la mayoría de viviendas de adobe de las localidades de Calacoa, San Cristóbal, Cuchumbaya, Solajo, Carumas, Soquesane y otros. Los daños ocasionados son principalmente agrietamientos de las paredes y caídas de sus fachadas. Muchos de los agrietamientos se produjeron durante los sismos de mayo de 1999, y junio del 2001, y se han reactivado a raíz de los movimientos sísmicos de octubre último. Después de ocurrido el sismo y durante un periodo aproximado de 30 días, se ha producido un gran número de replicas (sismos menores asociados) que causaron...

Microtremor exploration was performed around seismic recording stations at five sites in Lima city, Peru in order to know the site amplification at these sites. The Spatial Autocorrelation (SPAC) method was applied to determine the observed phase velocity dispersion curve, which was subsequently inverted in order to estimate the 1-D S-wave velocity structure. From these results, the theoretical amplification factor was calculated to evaluate the site effect at each site. S-wave velocity profiles at alluvial gravel sites have S-wave velocities ranging from ∼500 to ∼1500 m/s which gradually increase with depth, while Vs profiles at sites located on fine alluvial material such as sand and silt have Swave velocities that vary between ∼200 and ∼500 m/s. The site responses of all Vs profiles show relatively high amplification levels at frequencies larger than 3 Hz. The average transfer...