Quick building damage assessment following disasters such as large earthquakes serves to establish a preliminary estimation of losses and casualties. These datasets are completed by employing several crowdsourcing initiatives, in which volunteers and collaborators map damaged buildings in a given area at a qualitative damage scale based on a post-earthquake aerial or satellite image. Automating this process is a temptation and a technical issue, but manual interpretation remains essential, with the identification of moderate and lateral damage being the key and limiting factor. Following the Haiti 2010 earthquake, many studies were completed by crossing multilayer data gathered from different sources (satellite, aerial, and field survey). These works created a building damage dataset that enabled the construction of different sets of empirical vulnerability functions. In the present study, we proposed to review the datasets used for the damage assessment again, investigate how they can be managed for understanding urban damage patterns, and quantify the potentialities and limits of the sets.A high-resolution map of damage in Port-au-Prince was used to obtain a deducted map of intensity and was then compared to more detailed post-earthquake investigations such as the microzonation of the city (Belvaux et al. 2018). These detailed post-earthquake investigations, in which array microtremor measurements are performed for characterization of the subsurface soil, contribute to a better understanding of local variations in intensity. Subsequently, a retro damage scenario was run, considering the different sets of vulnerability functions (using the RISK-UE methodology vulnerability indexes) fitted with empirical vulnerability functions. Using the characterization of the exposure on a remote sensing basis, the results fit the heaviest damage well (building collapse), but they overestimated moderate damage states compared to the observations. However, is an aerial image based dataset sufficiently exhaustive for moderate damage, which is mostly visible from a lateral or internal point of view? Finally, we suggested some range of adjustments that can be applied to a vulnerability assessment originating from remote sensing data such that it can be used more accurately in the detection of urban damage, even for moderate damage degrees.

ResumenEste estudio está enfocado a la caracterización de efectos sísmicos locales en la ciudad de Lorca y corresponde a uno de los aspectos de interés de una campaña de intervención post-sísmica organizada por Institut Geològic de Catalunya (IGC), la Universitat Politécnica de Catalunya (UPC), la Asociación Española de Ingeniería Sísmica (AEIS) conjuntamente con las asociaciones de ingeniería sísmica francesa (AFPS) y portuguesa (SPES) con el objetivo de calibrar, verificar y validar las metodologías de evaluación del riesgo sísmico que estos organismos utilizan. Se presenta el trabajo realizado y los resultados obtenidos para caracterizar la capa de suelos blandos aplicando dos técnicas basadas en medidas de ruido sísmico ambiental: la técnica del cociente espectral H/V y la técnica de "array". El registro de réplicas en distintos emplazamientos ha permitido obtener la respuesta sísmica de estos sitios. A partir de la información obtenida en los trabajos geofísicos de campo se han definido columnas de suelo representativas, se ha podido clasificar el tipo de suelo según el Eurocódigo 8, se ha modelizado su respuesta sísmica y se ha estimado el incremento de intensidad macrosísmica debido a la presencia de suelos blandos. Palabras clave: Efectos locales, ruido sísmico, Vs30, EC8, Simulación numérica, Sismo de Lorca. Site effects characterization in Lorca city AbstractThis study is focused on the characterization of seismic local effects in Lorca city. This aspect fits to one of the interesting points of a field survey for a post-seismic inspection organized by Institut Geològic of Catalonia (IGC), the Universitat Politècnica of Catalonia (UPC), the Spanish Association of Seismic Engineering (AEIS) together with the Earthquake Engineering Associations of France (AFPS) and Portugal (SPES) with the aim to calibrate, check and validate methodologies for seismic risk assessment that these organisms use. We present the work done and the obtained results in order to characterize the soil layers applying two passive seismic techniques: the H/V spectral ratio and the array method. The record of aftershocks in different emplacements has allowed us to obtain the soil seismic response of these sites. The information obtained from the geophysical field survey allowed the definition of representative soil columns and the soil classification according the Eurocode 8. Subsequently, the soil seismic response has been modelled and the increase of macroseismic intensity due to the presence of soft soils has been assessed.

Seismic crisis occurred in Lorca (Murcia) on 11 th May 2011 originated an important number of accelerograms recorded in the IGN stations. The analysis of uniformly computed parameters has produced interesting results for Earthquake Engineering, in particular those recorded in Lorca. Strong ground motion has been specially observed in the horizontal component perpendicular to the Alhama de Murcia fault, at the origin of the earthquake. Values of PGA= 0,37g and CAV= 0.27g•s seems to be compensated by a short duration of the motion producing a macroseismic Intensity not greater than VII in Lorca. The contribution of near field component of ground motion due to the rupture propagation to and under the Lorca town was shown on acceleration, velocity and displacement time series and also on elastic response spectra.

In this paper, we describe recent studies for the geophysical and geomechanical characterization of soils in Hispaniola (Greater Antilles), an island threatened by the eventual rupture of major seismogenic fault systems. The investigations were performed for four different cities settled on complex geological formations in Haiti (Cap-Haïtien, Port-au-Prince) and the Dominican Republic (Santo Domingo, Santiago de los Caballeros). We present the complete methodology we implemented for mapping zones of homogeneous seismic response and for microzonation studies, but each main stage of investigation is described as it was conducted in one or two cities. Therefore, first we present our site-characterization technique applied to Santo Domingo and Santiago de los Caballeros, which is based on geotechnical data, geophysical multichannel analysis of surface waves, and ambient-noise recordings. Then we present the site-response analysis through numerical analysis with nonlinear soil models that we performed for the city of Cap-Haïtien. Finally, we describe the amplification factors for site-specific response spectra that we derived for the microzonation of Port-au-Prince. We argue for the implementation of a multidisciplinary approach built upon complementary field geological, geophysical, and geotechnical data rather than solely depending on geophysical measures for the characterization of VS30. In addition, we explore the compatibility of the soil classes recommended by the International Building Code (IBC) in the context of local seismic amplification.

On 11 May 2011 an earthquake of magnitude 5.2 ( M w) hit the Murcia region of Spain causing significant damage to buildings in the town of Lorca. Accelerograms were recorded by stations of the Instituto Geográfico Nacional, and high-amplitude ground motions were observed at the Lorca station, with a peak ground acceleration (PGA) of 0.37 g. The contribution of a near-field component of ground motion is shown in time histories and in elastic response spectra. Features of near-field ground motions such as directivity could have significantly enhanced the ground shaking caused by this event. Local amplification effects in Lorca were investigated by the H/V spectral ratio technique and an array method. Information obtained from the geophysical field survey allowed the definition of representative soil columns and site classifications according to Eurocode 8. Modeling of site response is conducted for an example location. The aftershocks recorded at different sites confirm the soil amplification at these locations.