Laserfiche WebLink
CHAPTER 10. EARTHQUAKE <br />10-15 <br /> <br />Figure 10-8. Liquefaction Susceptibility for Kittitas County <br />10.2.3 Frequency <br />Because of its location at the boundary of two major tectonic plates, Washington State is particularly <br />vulnerable to earthquakes. FEMA has determined that Washington State ranks second (behind only <br />California) among states most susceptible to damaging earthquakes. According to the Washington State <br />Enhanced Hazard Mitigation Plan, the probability of future occurrence for earthquakes similar to the 1965 <br />Magnitude 6.5 Seattle-Tacoma event and the 2001 Magnitude 6.8 Nisqually event is about once every 35 <br />years. The USGS has estimated that there is an 84-percent chance of a Magnitude 6.5 or greater deep <br />earthquake over the next 50 years. <br />The USGS Unified Hazard Tool shows that there is a 2 percent chance annually of a level IV earthquake <br />(on the Modified Mercalli Scale) occurring within 50 kilometers of Kittitas within the next 50 years. The <br />largest earthquake within 100 miles of Kittitas was a Magnitude 5.5 event in 1996. Annual earthquake <br />probabilities for different peak ground accelerations within 50 kilometers of the planning area over the next <br />50 years are shown in Table 10-4.