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CHAPTER 10. EARTHQUAKE <br />10-8 <br />amplification corrections. Color-coded instrumental intensity maps are derived from empirical relations <br />between peak ground motions and Modified Mercalli intensity. Two types of shake map are typically <br />generated from the data: <br />• A probabilistic seismic hazard map shows the hazard from earthquakes that geologists and <br />seismologists agree could occur. The maps are expressed in terms of probability of exceeding <br />a certain PGA, such as the 10-percent probability of exceedance in 50 years. This level of <br />ground shaking has been used for designing buildings in high seismic areas. <br />• Earthquake scenario maps describe the expected ground motions and effects of hypothetical <br />large earthquakes for a region. Five scenarios were chosen for this plan: <br />• Cle Elum Fault Scenario—A Magnitude 6.8 event with a shallow depth and epicenter located <br />13 miles southwest of Ellensburg (see Figure 10-2) <br />• Horse Heavens Scenario—A Magnitude 7.1 event with an epicenter southwest of Yakima, WA <br />(see Figure 10-3) <br />• Mill Creek Scenario—A Magnitude 7.1 event with an epicenter southwest of Kennewick, WA <br />(see Figure 10-4) <br />• Rattlesnake Wallula Scenario—A Magnitude 7.4 event with an epicenter east of I-82, near <br />Kennewick, WA (see Figure 10-5) <br />• Saddle Mountain Fault Scenario—A Magnitude 7.3 event with an epicenter 23 miles southeast <br />of Ellensburg (see Figure 10-6)