Abstract
This paper presents the general results in terms of maps, as well as geological and numerical models of a site effect study, that aimed at a better understanding of the ground motion amplification on the Gros-Morne hill, in the southeastern part of Port-au-Prince, Haiti, which might have influenced the 2010 event damage pattern in that area. These maps and models are based on multiple geophysical–seismological survey outputs that are presented, in detail, in Part A of this publication. Those outputs include electrical resistivity tomography sections, P-wave velocity profiles, S-wave logs, estimates of the fundamental resonance frequency for many locations, as well as earthquake recordings at three sites and associated site amplification assessment for the top of the hill. Related results are discussed in Part A with respect to outputs and interpretations that had been published earlier by other research teams for the same site. Our results only partly confirm the strong seismic amplification effects highlighted by some of the previous studies for this hill site, which had been attributed to the influence of local topographic and soil characteristics on seismic ground motion. Here, we focus on the imaging of different site effect components over the entire survey area; we present maps of shear wave velocity variations, of changing fundamental resonance frequencies, and of related estimates of soft soil/rock thickness, of peak spectral amplitudes, and of ambient ground motion polarization. Results have also been compiled within a 3D surface–subsurface model of the hill, which helps visualize the geological characteristics of the area, which are relevant for site effect analyses. From the 3D geomodel, we extracted one 2D geological section along the short-axis of the hill, crossing it near the location of Hotel Montana on top of the hill, which had been destroyed during the earthquake, and has now been rebuilt. This cross-section was used for dynamic numerical modelling of seismic ground motion, and for related site amplification calculation. The numerical results are compared with the site amplification characteristics that had been estimated from the ambient vibration measurements and the earthquake recordings.
Highlights
Haiti is crossed by several active faults that give rise to a substantial seismic hazard in Haiti ([1]), which can reach peak ground motion acceleration of 0.4 g for a 475-year return period in the vicinity of those faults
The extended use of horizontal verticalspectral spectral ratio ratio (HVSR) is strongly dependent on other geophysical outputs, such as shear wave velocity data, that are needed for thickness calculation
To explain this limited use of HVSR amplitude information, we compare in Figure 9 the 2D modelled standard spectral ratio (SSR) with the HVSR and with the NS S-waves HVSR that had been measured near Hotel Montana site
Summary
Haiti is crossed by several active faults that give rise to a substantial seismic hazard in Haiti ([1]), which can reach peak ground motion acceleration of 0.4 g for a 475-year return period in the vicinity of those faults. Thebeen extent of the disaster by this event cannot purely be explainedcauses by of thethose widespread such as the high In building vulnerability and locally amplified ground regional destruction, seismic hazard characteristics. In the hilly areas in the southern part of Port-au-Prince, and in particular, to more intense damage study is focused onlocation this latterineffect, especially on site that might have contributed on the hillOur of Gros-Morne Port-au-Prince, and in particular, on of referred to possible site amplification in order to explain the severe damage in some zones on top the hill of Gros-Morne (see location in Figure 1 below). For this site, several previous studies referred.
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