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We describe a simple model for prediction of macroseismic intensities adapted to Guadeloupe and Martinique (Lesser Antilles), based on a combination of peak ground acceleration (PGA) predictive equation and a forward relation between acceleration and intensity. The PGA predictive equation is built from a 3-parameter functional form constrained by measurements from permanent accelerometer stations, mostly associated with Les Saintes crustal earthquake (21/11/2004, M w = 6.3) and its many aftershocks. The forward intensity model is checked on a database of recent instrumental events of various origins with magnitudes 1.6 to 7.4, distances from 4 to 300 km, and observed intensities from I to VIII. Global sigma residual equals 0.8 in the MSK scale, suggesting a larger applicability range than the intermediate PGA predictive equation. The model is presently used by the French Lesser Antilles observatories to produce automatic reports for earthquakes potentially felt. Résumé Nous proposons un modèle simple de prédiction des intensités macrosismiques adapté à la Guadeloupe et à la Martinique (Petites Antilles) basé sur la combinaison d'une loi d'atténuation des accélérations horizontales maximales (PGA) et d'une relation directe entre accélération et intensité. Le modèle prédictif des PGA est contruit à partir d'une équation fonctionnelle à 3 paramètres contrainte par des données provenant de stations accélérométriques permanentes principalement associées au séisme des Saintes (21/11/2004, M w = 6.3) et ses nombreuses répliques. Le modèle prédictif d'intensité est testé sur une base de données instrumentale de séismes récents, de magnitudes 1.6 à 7.4, distances 4 à 300 km et intensités observées entre I et VIII. Le résidu RMS final est de 0.8 sur l'échelle MSK, ce qui suggère un plus large domaine d'applicabilité que le modèle intermédiaire des PGA. Le modèle est actuellement utilisé par les observatoires des Antilles françaises pour produire des communiqués semi-automatiques lors de séismes susceptibles d'être ressentis. . Phone : +33 1 83 95 75 28. Fax : +33 1 83 95 77 17 Email address: beauducel@ipgp.fr (François Beauducel)deformed Caribbean plate with shallow crustal seismicity from 2 km up to 15-20 km in depth. Very shallow earthquakes occurring below/or very close to Guadeloupe archipelago islands can be felt sometimes with magnitude less than 2.0.

International audienc

International audienceWe consider some practical issues of the determination of the b-value of sequences of magnitudes with the bootstrap method for short series of length L and various quantization levels Dm of the magnitude. Preliminary Monte Carlo tests performed with Dm ¼ 0 demonstrate the superiority of the maximum likelihood estimator bMLE, and the inconsistency of the, yet often used, bLR estimator defined as the least-squares slope of the experimental Gutenberg-Richter curve. The Monte Carlo tests are also applied to an estimator, bKS, which minimizes the Kolmogorov-Smirnov distance between the cumulative distribution of magnitudes and a power-law model. Monte Carlo tests of discrete versions of the bMLE and bKS estimators are done for Dm ¼ f0:1; 0:2; 0:3g and used as reference to evaluate the performance of the bootstrap determination of b. We show that all estimators provide b estimates within 10 % error for L C 100 and if a large number, n = 2 9 105, of bootstrapped sample series is used. A resolution test done with Dm ¼ 0:1 reveals that a clear distinction between b = 0.8, 1.0, and 1.2 is obtained if L= 200

No abstract