Lima, Peru's capital, has about 9.6 million inhabitants and keeps attracting more residents searching for a better life. Many citizens, without access to housing subsidies, live in informal housing and shack settlements. A typical social phenomenon in Lima is the sudden illegal occupation of areas for urban settlements. When such areas are unsafe against natural hazards, it is important to relocate such a population to avoid significant future losses. In this communication, we present an application of Sentinel-1 synthetic aperture radar (SAR) images to map the extension of a recent occupation of an area with unfavorable soil conditions against earthquakes.

The Lima metropolitan area is in a prone earthquake zone, which is exposed to a seismic gap; this can result in Mw 8.9 megathrust earthquake in the central Peru. After the Pisco earthquake in 2007, risk management policies changed in Peru and are improving annually. Thus, more resources are destinated to assessing earthquake hazard, vulnerability, and risk in districts of the Lima metropolitan area mainly; nevertheless, they are limited to cover in detailed the whole extension of probable affected area after this potential megathrust earthquake. Data of buildings in the Lima metropolitan area were analyzed in this paper, to provide useful information in the development of rapid methodologies of identification of buildings. The Japan Peru Center for Earthquake Engineering and Disaster Mitigation (CISMID) gathered these data from 2010 to 2021 in field surveys to conduct vulnerability and risk studies; the survey of building characteristics consisted of obtain mainly the number of stories, predominant material, structural systems, type of occupancy, and state of conservation. Vulnerability and risk studies for districts of the Lima metropolitan area were conducted by considering one representative building in one block. Results showed that the predominant material in the Lima metropolitan area is masonry, used in different structural systems, such as confined masonry and other which are nonengineered structures. Also, two-story buildings are predominant in the target area, followed by one and three-stories buildings. Risk assessment for the Lima metropolitan area and the study area were conducted using the data from the characterization of structural typologies obtained in this study. Approximately, 47.72% and 58.67% of buildings presented a very high-risk level in the Lima metropolitan area and the study area, respectively, under the expected earthquake scenario due to the seismic gap in the central Peru.

In Peru, the most commonly used structural system for housing construction is based on confined masonry walls. Solid engineered walls are regulated by the NTE-E070 standard, which lays down a required degree of earthquake resilience. However, around 60% of the population lives in non-engineered houses that use tubular blocks for their walls. This paper presents a comparison of the behaviors of non-engineered tubular block walls and solid engineered walls. Tests were performed on a tubular brick wall by subjecting it to horizontal cyclic loading to examine the effects under a constant axial load of 20 tf. Then, the test results were compared with those for walls in the CISMID Structural Lab database. The resistance of the tubular brick wall in terms of shear stress was found to be relatively low, having an average value of 4 kg/cm², while the solid walls can withstand a shear stress in excess of 5.5 kg/cm².

Evaluation of site amplification factors (SAFs) of seismic waves has been one of the important issues for evaluating seismic hazards. The authors have proposed a deep neural network (DNN) model in order to cost-effectively and accurately estimate SAF from microtremor horizontal-to-vertical spectral ratio (MHVR). In this study, we assessed the SAFs in southern Lima, Peru by estimating from MHVRs and DNN. First, we validated the applicability of the DNN model to Lima by estimating the SAFs from the MHVRs observed at seismic stations in Lima. From the comparison with the observed SAFs derived from spectral inversion technique, we confirmed that the SAFs in Lima were accurately estimated by the DNN model. The SAFs in the southern Lima including Chorrillos and Villa El Salvador districts were evaluated by applying the DNN model to the observed MHVRs at approximately 250 sites. We found that large amplifications at low frequency around 1 Hz were expected in the southeastern coastal areas formed by eolian sands whereas smaller amplification were estimated in the northwestern areas mainly located on alluvial deposits.

During big earthquakes, one of the challenges for the decision maker is the estimation of the resources for the attention of the disaster which is computed based on the casualties and injured people, which is generated by damaging earthquake. In this investigation, two criteria for the estimation of casualties during damaging earthquake were presented forMw>6.5 in one target area, namely, Chorrillos district in the Lima metropolitan. First criterion considers the compilation of existing data that reports the casualties on damaged cities with a population density involved, considering the lifestyle, the time of occurrence, the season of the year, that could influence in the number of victims, which is normalized to avoid temporary effects in the estimation. The second criterion considers the output generated prior computed process such earthquake hazard, microzoning and risk analysis of the target area. Here a series of identification of parameters has been computed such as location of the source of earthquake, depth and epicentral distance, distribution of population, social levels, and others, to estimate the risk. For the computing of the number of casualties in the affected area, a relation between the magnitude and risk is developed. Both criteria provided results which with an uncertain measure, but not so far from each other. That gives us confidence in this approach. Also, we evaluate the estimation with the major earthquake’s scenarios for the region especially in Peru, with reasonable results.