A preliminary investigation of strong-motion data from the French Antilles

Abstract

Strong-motion networks have been operating in the Caribbean region since the 1970s, however, until the mid-1990s only a few analogue stations were operational and the quantity of data recorded was very low. Since the mid-1990s, digital accelerometric networks have been established on islands within the region. At present there are thought to be about 160 stations operating in this region with a handful on Cuba, 65 on the French Antilles (mainly Guadeloupe and Martinique), eight on Jamaica, 78 on Puerto Rico (plus others on adjacent islands) and four on Trinidad.After briefly summarising the available data from the Caribbean islands, this article is mainly concerned with analysing the data that has been recorded by the networks operating on the French Antilles in terms of their distribution with respect to magnitude, source-to-site distance, focal depth and event type; site effects at certain stations; and also with respect to their predictability by ground motion estimation equations developed using data from different regions of the world. More than 300 good quality triaxial acceleration time-histories have been recorded on Guadeloupe and Martinique at a large number of stations from earthquakes with moment magnitudes larger than 4.8, however, most of the records are from considerable source-to-site distances. From the data available it is found that many of the commonly-used ground motion estimation equations for shallow crustal earthquakes poorly estimate the observed ground motions on the two islands; ground motions on Guadeloupe and Martinique have smaller amplitudes and are more variable than expected. This difference could be due to regional dependence of ground motions because of, for example, differing tectonics or crustal structures or because the ground motions so far recorded are, in general, from smaller earthquakes and greater distances than the range of applicability of the investigated equations.

Comparing predicted and observed ground motions from subduction earthquakes in the Lesser Antilles

“…In a previous article Douglas et al [2006] examined the ability of various GMPEs to accurately predict shaking from crustal and subduction earthquakes recorded on the French Antilles (Guadeloupe and Martinique). They found that for crustal earthquakes none of the nine considered GMPEs closely predicted the observed ground motions nor their variabilities.…”

“…For subduction earthquakes (both interface and intraslab) Douglas et al [2006] considered three often-used models developed using data from subduction zones worldwide: Atkinson and Boore [2003], Crouse [1991] and Youngs et al [1997], and found that the model of Youngs et al [1997] predicts reasonably well earthquake ground motions recorded on the French Antilles but the other two models poorly predict such motions. The majority of the records used by Douglas et al [2006] for subduction earthquakes were from interface events: 91 records from eleven interface earthquakes compared to 56 records from three intraslab earthquakes. Consequently the results obtained may better reflect the ability of the three examined models to estimate ground motions from interface events rather than intraslab earthquakes.…”

“…Given the importance of deep intraslab earthquakes in the Lesser Antilles, in this short article we extend the intraslab dataset used by Douglas et al [2006] by the addition of six strong-motion records from the strong-motion network on the island of Trinidad to the south of Guadeloupe and Martinique and one record from a station on Dominica between Guadeloupe and Martinique. In addition, since the study of Douglas et al [2006] was completed three other intraslab earthquakes have been well recorded by the extensive strong-motion networks on Guadeloupe and Martinique, including that of the 29th November 2007, and, therefore, these data have been included in the analysis.…”

“…In addition, since the study of Douglas et al [2006] was completed three other intraslab earthquakes have been well recorded by the extensive strong-motion networks on Guadeloupe and Martinique, including that of the 29th November 2007, and, therefore, these data have been included in the analysis. In total, the intraslab strong-motion dataset from the Lesser Antilles consists of 146 records from nine earthquakes.…”

“…In total, the intraslab strong-motion dataset from the Lesser Antilles consists of 146 records from nine earthquakes. In addition, the interface strong-motion dataset of Douglas et al [2006] is extended by the inclusion of 68 records from three interface events that occurred since the completion of the original study. Recently a number of robust GMPEs for subduction zones have been published and, therefore, in this article we examine the applicability of five new ground-motion models in addition to the three models originally tested.…”