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TitreModified mercalli intensities for nine earthquakes in central and western Washington between 1989 and 1999
AuteurBrocher, T M; Dewey, J W; Cassidy, J F
SourceUnited States Geological Survey, Open-file Report no. 2017-1104, 2017, 82 pages, https://doi.org/10.3133/ofr20171104
Année2017
Séries alt.Secteur des sciences de la Terre, Contribution externe 20160102
ÉditeurUnited States Geological Survey
Documentdossier public
Lang.anglais
DOIhttps://doi.org/10.3133/ofr20171104
Mediapapier; en ligne; numérique
Formatspdf
Lat/Long OENS-124.0000 -119.0000 49.0000 44.7500
Sujetssecousses séismiques; données sismiques; sismicité; tectonique
Illustrationslocation maps; graphs; tables
ProgrammeOuest du Canada, risque géoscience, Géoscience pour la sécurité publique
Résumé(disponible en anglais seulement)
We determine Modified Mercalli (Seismic) Intensities (MMI) for nine onshore earthquakes of magnitude 4.5 and larger that occurred in central and western Washington between 1989 and 1999, on the basis of effects reported in postal questionnaires, the press, and professional collaborators. The earthquakes studied include four earthquakes of M5 and larger: the M5.0 Deming earthquake of April 13, 1990, the M5.0 Point Robinson earthquake of January 29, 1995, the M5.4 Duvall earthquake of May 3, 1996, and the M5.8 Satsop earthquake of July 3, 1999. The MMI are assigned using data and procedures that evolved at the U.S. Geological Survey (USGS) and its Department of Commerce predecessors and that were used to assign MMI to felt earthquakes occurring in the United States between 1931 and 1986. We refer to the MMI assigned in this report as traditional MMI, because they are based on responses to postal questionnaires and on newspaper reports, and to distinguish them from MMI calculated from data contributed by the public by way of the internet. Maximum traditional MMI documented for the M5 and larger earthquakes are VII for the 1990 Deming earthquake, V for the 1995 Point Robinson earthquake, VI for the 1996 Duvall earthquake, and VII for the 1999 Satsop earthquake; the five other earthquakes were variously assigned maximum intensities of IV, V, or VI. Starting in 1995, the Pacific Northwest Seismic Network (PNSN) published MMI maps for four of the studied earthquakes, based on macroseismic observations submitted by the public by way of the internet. With the availability now of the traditional USGS MMI interpreted for all the sites from which USGS postal questionnaires were returned, the four Washington earthquakes join a rather small group of earthquakes for which both traditional USGS MMI and some type of internet-based MMI have been assigned. The values and distributions of the traditional MMI are broadly similar to the internet-based PNSN intensities; we discuss some differences in detail that reflect differences in data-sampling procedure, differences in the procedure used to assign intensity numbers from macroseismic observations, and differences in how intensities are mapped.
Résumé(Résumé en langage clair et simple, non publié)
Ce rapport documente estimé rapports d'intensité de l'État de Washington et la Colombie-Britannique pour trois séismes modérés qui se sont produits dans les années 1990. Ces tremblements de terre (magnitude 5 à 5,8) ont été ressenties à travers Washington, nord de l'Oregon, et le sud de la Colombie-Britannique. En intégrant des données d'intensité de l'ensemble de ces régions, nous fournissons une base de données améliorée qui peut être utilisé pour évaluer historiques (pré-instrumental) tremblements de terre (pour lequel ressenti information existe, mais pas des enregistrements sismiques) et de mieux estimer les impacts de futurs tremblements de terre à Washington et en Colombie-Britannique. Cela contribuera à des modèles de tremblement de terre et de danger améliorées pour le sud de la Colombie-Britannique.
GEOSCAN ID298867