thumbnail

Modified mercalli intensities for nine earthquakes in central and western Washington between 1989 and 1999

Open-File Report 2017-1104
By: , , and 
https://doi.org/10.3133/ofr20171104

Links

Abstract

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.

Suggested Citation

Brocher, T.M., Dewey, J.W., and Cassidy, J.F., 2017, Modified Mercalli Intensities for nine earthquakes in central and western Washington between 1989 and 1999: U.S. Geological Survey Open-File Report 2017–1104, 82 p., https://doi.org/10.3133/ofr20171104.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract 
  • Introduction
  • Traditional USGS Postal Canvasses and Interpretation of MMI 
  • Nine Washington State Earthquakes Between 1989 and 1999 
  • The 1987 to Early 2000s Gap in Reporting MMI
  • Purposes of this Report 
  • Comparing Traditional MMI to Community Internet Intensity Reports
  • Format of the Remainder of this Report
  • M4.5 1989 Olympic Peninsula Earthquake
  • M4.5 1989 Okanogan Earthquake
  • M4.9 1989 Morton Earthquake 
  • M5.0 1990 Deming Earthquake 
  • M5.0 1995 Point Robinson Earthquake 
  • M5.2 1996 Duvall Earthquake
  • M4.9 1997 Bremerton Earthquake
  • M4.6 1997 Okanogan Earthquake
  • M5.8 1999 Satsop Earthquake 
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Modified mercalli intensities for nine earthquakes in central and western Washington between 1989 and 1999
Series title Open-File Report
Series number 2017-1104
DOI 10.3133/ofr20171104
Year Published 2017
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Earthquake Science Center
Description v, 82 p.
Country United States
State Oregon, Washington
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details