hazard identification and vulnerability analysis - Mason County

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included in disaster preparedness classes. Although much work has been done on disaster preparedness for public, local governments, emergency planners and the citizens, they need to recognize the dangers and effects of tsunamis and seiches as a component of the earthquake hazard. Resources National Oceanic and Atmospheric Administration National Weather Service United States Geological Survey Washington State Department of Natural Resources 49
VOLCANOS/ASH FALL Definition A volcano is a vent in the earth’s crust through which magma, rock fragments, gases, and ash are ejected from the earth’s interior. A volcanic mountain is created over time by the accumulation of these erupted products on the earth’s surface. History There are no volcanoes in Mason County, however, the proximity to potentially active volcanoes in the Cascade Mountains to the east could impact the county. When Mt. St. Helens erupted on May 18, 1980, heavy ash from a west wind blanketed much of Eastern Washington. Subsequent eruptions on May 25 and June 12 similarly affected Western Washington, although to a lesser degree. Fifty seven people were killed during this 5.1 magnitude eruption. Mount Rainier volcano in Washington State is one of the Nation’s most dangerous volcanoes. More than 100,000 people live in areas near Rainier that have been buried by volcanic debris flows during the past few thousand years. Mason County’s location with respect to the active volcanoes would limit the number of volcano hazards, however impacts would be felt. The economic, cultural and transportation impacts that would be experienced in Mason County, however, would be severe if such an eruption were to occur on Mount Rainier. Interstate 5 and Interstate 90 would be closed, thus disrupting key routes for trade and travel. Ash and some debris could fall on Mason County depending on prevailing winds at the time. The County could serve as a site for displaced residents for not only days, but perhaps for decades to come, thus impacting the infrastructure and resources. Puget Sound fishing resources and economic foundations of the timber and recreation industries could be impacted for decades. The tourism industry and economic benefits derived could also be affected for Mason County. Hazard Identification and Vulnerability Assessment Volcanoes commonly repeat their past behavior. It is likely that the types, frequencies, and magnitudes of past activity will be repeated in the future. Volcanoes usually exhibit warning signs that can be detected by instruments or observations before erupting. However, explosions caused by heated material coming into contact with ground water can happen without warning. In the future Washington State can expect volcanoes avalanches, lahars (mudflows), lava flows, pyroclastic flows, and tephra falls, and collapse of a sector of a volcano 50
Page 1 and 2: MASON COUNTY HAZARD IDENTIFICATION
Page 3 and 4: Seattle, 20 miles northwest of Olym
Page 5 and 6: Mason County, due to its location a
Page 7 and 8: Resources United States Geological
Page 9 and 10: HISTORY VI. Felt by all; many frigh
Page 11 and 12: America, the Juan de Fuca plate sli
Page 13 and 14: Puget Sound basin would directly af
Page 15 and 16: Subduction Zone Earthquakes: Althou
Page 17 and 18: Conclusions Mason County will exper
Page 19 and 20: FLOODING Definition: An inundation
Page 21 and 22: ATTACHMENT I SKOKOMISH RIVER BASIN
Page 23 and 24: ATTACHMENT III SATOP RIVER BASIN 22
Page 25 and 26: normal part of most forest and rang
Page 27 and 28: LAND SHIFT (SLIDES / EROSION) Defin
Page 29: HIGHWAY 101 MAJOR SLIDE AREAS (Sout
Page 38: SLIDE AREAS ALONG HIGHWAY 3 37
Page 43 and 44: HARSTEME ISLAND SLIDE AREAS 42
Page 45 and 46: SEVERE STORMS Definition Severe sto
Page 47 and 48: The most severe snowstorms that hav
Page 49: TSUNAMI, HIGH WAVES, SEICHES Defini
Page 53 and 54: • Magma or molten rock or lava or
Page 55 and 56: Conclusion volcano. Examples of suc
Page 57 and 58: its three 27,000 kilowatt generator
Page 59 and 60: Major petroleum shortages developed
Page 61: History Hazardous material incident

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