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2025 Hazard Mitigation Plan <br />Kittitas County, Washington <br /> <br /> <br />Chapter 4: Hazard Identification and Risk Assessment 113 <br />warning will arrive faster than someone that is further away. Table 4-51 outlines the alerting thresholds <br />for the ShakeAlert Earthquake Early Warning system.137F <br />137, <br />138F <br />138 <br />Table 4-51. ShakeAlert Earthquake Early Warning System Alerting Thresholds <br />Warning System Threshold <br />Wireless Emergency Alerts <br />The Wireless Emergency Alerts are used in response to magnitude 5.0 or <br />greater earthquakes and will alert people who will experience a shaking level of <br />MMI IV (light) or greater. <br />MyShake App <br />The MyShake App is used in response to magnitude 4.5 or greater earthquakes <br />and will alert people who will experience a shaking level of MMI III (weak) or <br />greater. <br />Android Alerts <br />The Android Alerts are used in response to magnitude 4.5 or greater <br />earthquakes and will alert people who will experience a shaking level of MMI III <br />(weak) or greater. <br />4.6.4.4. Probability and Frequency <br />The probability of occurrence for an earthquake in Kittitas County is medium because significant <br />occurrences of this hazard have impacted the County and will likely occur again within 25 years. Due to <br />Washington’s location at the boundary of two (2) major tectonic plates, the State is particularly vulnerable <br />to earthquakes. USGS estimates that there is an 84% chance of a magnitude 6.5 or greater deep <br />earthquake occurring over the next 50 years in the Pacific Northwest.139F <br />139 According to the 2023 <br />Washington State Enhanced Hazard Mitigation Plan, the probability of future earthquake related disaster <br />declarations each year is 2.5% in the State.140F <br />140 <br /> <br />The USGS National Seismic Hazard Maps reflect the best and most current understanding of earthquake <br />hazard in an area, the distribution of damaging earthquake shaking across the United States, and <br />compares earthquake shaking hazard areas with other areas across the United States. Figure 4-14 <br />illustrates the most recent USGS National Seismic Hazard Map which represents the expected number <br />of occurrences of damaging earthquake shaking in 10,000 years. A “damaging earthquake shaking” in <br />this map is that of MMI level VI or higher.141F <br />141 <br /> <br /> <br />137 California Governor’s Office of Emergency Services. (n.d.). Earthquake Warning California: Types of Alerts. <br />Retrieved from https://earthquake.ca.gov/get-alerts/. <br />138 Washington Emergency Management Division. (n.d.). Alert & Warning Notifications . Retrieved from <br />https://mil.wa.gov/alerts. <br />139 Pacific Northwest Seismic Network. (n.d.). Deep Earthquakes. Retrieved from <br />https://pnsn.org/outreach/earthquakesources/deepearthquakes . <br />140 Washington State Emergency Management Division. (2023). Washington State Enhanced Hazard Mitigation <br />Plan. Retrieved from https://mil.wa.gov/asset/651ec296d76a9/2023_WA_SEHMP_final_20231004.pdf . <br />141 United States Geological Survey, Earthquake Hazards Program. (2022). Introduction to the National Seismic <br />Hazard Maps. Retrieved from https://www.usgs.gov/programs/earthquake-hazards/science/introduction-national- <br />seismic-hazard-maps.