Site Effect Assessment of the Gros-Morne Hill Area in Port-au-Prince, Haiti, Part B: Mapping and Modelling Results

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.

Site Effect Assessment of the Gros-Morne Hill Area in Port-au-Prince, Haiti, Part A: Geophysical-Seismological Survey Results

“…Here, we will not further discuss the validity of our results with respect to previous measurements and to observed damage distributions. Some (simple) comparison with the latter will be provided in a follow-up paper by the same authors ( [31]); this comparison will be supported by additional overview maps of interpolated HVSR results, a 3D geomodel of Gros-Morne hill and a 2D numerical analysis of site effects for a central cross-section of the hill. In this paper, we mainly wanted to highlight the fact that a hill structure can be affected by multiple types of site effects that can vary over relatively short distances (over less than 200 m).…”

Site Effect Potential in Fond Parisien, in the East of Port-au-Prince, Haiti

“…These site effects were investigated at a regional scale for the whole agglomeration of Port-au-Prince [10,13]. More detailed studies were implemented by Hough et al [11], Assimaki and Jeong [12] and more recently by Ulysse et al [14,15] for a hilly area, Gros-Morne, located to the east of Port-au-Prince.…”

“…With regard to site effect, the city of Port-au-Prince and some of its neighboring areas have been studied by several groups among which Hough et al [11], Assimaki and Jeong [12] and St Fleur et al [13]. More recently, Ulysse et al [14,15], by integrating several investigation and modelling methods, provided small-scale distribution maps of the site effects throughout a hilly area located in the Southeast of Port-au-Prince. Overall of these studies were especially focused on the central part of the EPGF.…”

The evaluation of the adjacency effect on the seismic response of homogenous hills

“…Most researchers who have focused on topographic effects have concentrated on the distribution of ampli cation over single hill features, whereas what is seen in nature is often more complicated. It is known that 2D or 3D geological structures and rock weathering contribute signi cantly to the ampli cation of seismic ground motion (Buech et al, 2010;Havenith et al, 2002;Kamalian et al, 2007;Sohrabi-Bidar et al, 2016;Spudich et al, 1996;Ulysse et al, 2018) The effect of different parameters on the seismic responses of topographic features is also studied by several researchers, namely, wavelength (Kamalian et al 2008), site geometry (Sohrabi-bidar and Kamalian 2013; Poursartip et al 2017; Asimaki and Mohammadi 2018), wave type (Kawase 1988; Semblat et al 2000;Chaillat et al 2008) and material characteristics (Luzon et al 2009).…”