Most of buildings and structures are usually projected according to two main axes. However, the geographical position of these buildings varies randomly. Such random distributions of the azimuthal positions of structures, in most of the cities, generally, are not accounted for when assessing their seismic risk; certainly, the direction of the seismic loads is another highly random variable. Moreover, an additional important source of uncertainty is related to the structural response, mainly due to the random character of the mechanical properties. There is a consensus that uncertainties must be considered for adequately assessing the seismic risk of structures, but these directionality effects have not been deeply explored so far. In this article, the influence of the high uncertainty involved in these input variables on the expected seismic damage is analysed. Thus, an actual earthquake, which affected the southern part of Spain, is studied. Notably, damages on a group of affected buildings, located close to the epicentre, are analysed and discussed in detail. The results show that the influence of the random azimuthal position of structures is an important source of uncertainty and that it should be taken into account when estimating the expected seismic risk in urban areas.

Costa Rica is located at the boundary of four tectonic plates where the regularity of destructive earthquakes highlights the necessity of seismic hazard estimations. This study contains the most recent Probabilistic Seismic Hazard Assessment (PSHA) for Costa Rica, calculated with the largest and the most updated earthquake database from both—the Earthquake Engineering Laboratory and the National Seismological Network of the University of Costa Rica. For the PSHA, we updated the seismicity parameters for the upper plate, subduction interplate, and intraslab tectonic domains, characterized the upper‐plate zones by percentages of fault types, and used weighted ground‐motion models for each of the tectonic domains. The resulted maps of peak ground acceleration (PGA) at return periods of 475 yr (PGA‐475) and 2475 yr, as well as the spectral accelerations, show geographic trends that allow for the division of the country in four seismic hazard levels: (1) extremely high for the Nicoya, Osa, and Burica peninsulas, situated directly above the subduction interplate, where the PGA‐475 could be 0.55–1.20g; (2) very high for most of the Guanacaste Province, where the PGA‐475 may be 0.55–0.70g; (3) high for most of the country (∼41%) with PGA‐475 values of 0.40–0.55g, including Central Costa Rica and the capital city of San Jose; and (4) moderate for the Talamanca Cordillera and Northern Costa Rica, with PGA‐475 up to 0.40g. These ground‐motion values are 0.1–0.6g higher than the previous PSHA for the Pacific peninsulas, Guanacaste, and the southeastern Caribbean. Further, hazard curves, uniform hazard spectra, and a hazard disaggregation indicate that the seismic hazard is lower but more complex in San Jose than in Liberia—the largest city in Guanacaste.

In this article, we present a strong‐motion database from earthquakes recorded by the Earthquake Engineering Laboratory at the University of Costa Rica. The database consists of 2471 three‐component accelerograms from 155 digitally recorded events. It covers the last 20 yr of measurements, including records from the 5 September 2012 $Mw$ 7.6 Nicoya earthquake. The engineering and seismological communities can use this data either to conduct new research or to improve seismic hazard studies in the region. A catalog is also available with metadata of each record containing several intensity measures from the ground‐motion time histories.