WASHINGTON STATE EARTHQUAKE HAZARDS

Linda Lawrance Noson, Anthony Qamar, and Gerald W. Thorsen

WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCES
INFORMATION CIRCULAR 85
1988


Printed copies are available for $1.00 each from:
P.O. Box 47007
Olympia, WA 98504-7007
(360) 902-1450

CONTENTS

Summary

Introduction

What Are Earthquakes?

How Are Earthquakes Measured?

What Causes Earthquakes?
Where Do Earthquakes In Washington Occur? When and Where Will the Next Big Earthquake Occur?

What Causes Damage? Where Has Earthquake Damage Occurred In Washington State? How Can We Reduce Earthquake Losses In Washington?
Glossary

References Cited

Selected catalogs containing information about earthquakes in Washington and adjacent areas

Publications of the Federal Emergency Management Agency

ILLUSTRATIONS


Figure 1 . Block diagrams of fault types
Figure 2 . Diagrams of near-surface ground motions produced by seismic waves
Figure 3 . Map showing location of active seismograph stations in the Pacific Northwest in 1987
Figure 4 . Sketch of components and dimensions of a typical remote seismograph station
Figure 5 . Seismograms illustrating the range of ground motions commonly recorded in Washington and Oregon
Figure 6 . Method for calculating epicentral distance and magnitude of an earthquake
Figure 7 . Isoseismal map for the Seattle-Tacoma earthquake of 1965
Figure 8 . Map showing relation between major tectonic plates and earthquakes
Figure 9 . Cutaway view of the Earth
Figure 10 . Diagram illustrating three types of plate boundaries
Figure 11 . Cross sections of Washington showing plate convergence and earthquake hypocenter locations
Figure 12 . Map showing epicenters of selected earthquakes in the Pacific Northwest since 1960
Figure 13 . Map showing epicenters and dates of the largest Pacific Northwest earthquakes between 1872 and 1987 .23
Figure 14 . Map showing epicenters of Washington earthquakes recorded from 1982 to 1987 (Mc > 2.0)
Figure 15 . Map showing faults in Washington known to be active or thought to have been active in the last 10,000 years
Figure 16 . Aerial view of the Saddle Mountain faults near Lake Cushman, Olympic Peninsula
Figure 17 . Photograph showing evidence for subsidence in coastal Washington, buried marsh
Figure 18 . Photograph showing evidence for subsidence in coastal Washington, ghost forest
Figure 19 . Photograph of a landslide in fill near Olympia, 1965
Figure 20 . Photograph of landslide, Tacoma Narrows, 1949
Figure 21 . Photographs of road damage caused by liquefaction, Olympia, 1965
Figure 22 . Photograph of sand blows, Olympia, 1965
Figure 23 . Tide gage records showing tsunami waves from the 1964 Alaska earthquake
Figure 24 . Map showing tsunami damage in coastal Washington from the 1964 Alaska earthquake
Figure 25 . Photograph of stripped dunes, coastal Washington
Figure 26 . Diagram showing structural components of a building
Figure 27 . Photograph showing failure of unreinforced masonry during the 1965 earthquake
Figure 28 . Photograph of damage at the Fisher Flouring Mills, 1965
Figure 29 . Photograph of collapsed roof, Puyallup High School, 1949
Figure 30 . Photograph of a collapsed parapet wall, Olympia, 1949
Figure 31 . Photograph of a damaged chimney, Kelso, 1949
Figure 32 . Photograph of fallen light fixtures in an Olympia school, 1965
Figure 33 . Photograph of fallen library shelves, 1949
Figure 34 . Photograph of Boeing Company tapes scattered by the 1965 earthquake
Figure 35 . Photograph of windows broken in a Tacoma store by the 1965 earthquake
Figure 36 . Photograph of government files disturbed by the 1965 earthquake
Figure 37 . Photograph of damaged radio tower, 1949
Figure 38 . Photograph of damage at Lower Van Norman Dam, California, 1971
Figure 39 . Photograph of shifted ground in Seattle, 1965
Figure 40 . Photograph of damage at school entrance, Castle Rock, 1949
Figure 41 . Photograph of damage to Lafayette School, Seattle, 1949
Figure 42 . Photograph of damage at Washington State Training School for Boys, Chehalis, 1949. 51
Figure 43 . Photograph of damaged arch, Capitol Building, Olympia, 1949
Figure 44 . Maps prepared for Uniform Building Code showing Seismic Risk Zones, 1988
Figure 45 . Photographs of unreinforced masonry buildings in Port Townsend
Figure 46 . Sketch showing method of securing a home water heater
Figure 47 . Sketch of a child in the "drop and cover" position

TABLES


Table 1. Modified Mercalli Intensity Scale
Table 2. Largest known earthquakes felt in Washington
Table 3. Wave heights of some recent tsunamis recorded at selected West Coast tide gages
Table 4. What to do during an earthquake
Table 5. What to do after the shaking stops