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INVENTORY OF EXISTING CONDITIONS <br />REGIONAL SEISMIC CONDITIONS <br />The Eugene Airport is in a location that is prone to seismic events. Since 1931, the city of Eugene has <br />experienced 100 earthquakes within a 30 mile radius from the center of the city. However, out of the 100 <br />earthquakes, only six earthquakes had a magnitude 2.5 or greater, three occurred in the year 2015 alone. <br />Table 1-18 shows the Richter Scale which is used to measure the magnitude of the earthquake along with <br />the impact of the quake. Due to the location of where the Eugene Airport sits, it has the potential to be <br />exposed to a great earthquake, or “megaquake.” <br /> <br />TABLE 1-18 <br />RICHTER SCALE <br />Richter Scale <br />Richter MagnitudeImpact <br />1No real impact <br />2Smallest quake that a person can normally feel. <br />3Comparable to the vibrations of a passing truck. <br />4May break windows, cause small or unstable objects to fall. <br />Minor damage occurs, objects such as furniture would move and weak constructed areas would <br />5 <br />fold. <br />6Damage to well-built structures, severe damage to poorly built ones. <br />7Buildings displaced from foundations; cracks in the earth ungrounding pipes broken. <br />8Bridges destroyed, few structures left standing <br />9+Near-total destruction, waves moving through the earth visible with the naked eye. <br />Source: USGS, SMS Tsunami Warning <br /> <br />Note: The impact correlated with the Richter magnitude is determined based on modifications to the Mercalli Scale. The <br />Mercalli Scale is used to measure the amount of damage an earthquake can generate. <br /> <br />Just off the coast of the Pacific Ocean is an area called the Cascadia Subduction Zone (CSZ). The CSZ is a <br />tectonic plate convergent boundary, which spans the coast line from Vancouver Island to the northern <br />part of California. The CSZ is the location of where the Juan De Fuca Plate meets the North American <br />Plate. Figure 1-23 shows a graphical representation of the location of the CSZ and the direction the <br />tectonic plates are converging. The Juan de Fuca Plate is the seafloor and is comprised of heavier rocks <br />then the continental mass of the North American Plate. These two pieces are constantly pushing against <br />each other, which causes the seafloor to sink below North America. <br /> <br />EUGENE AIRPORT MASTER PLAN 1-72 <br /> <br />