Utah Engineers Journal 2021 Issue

52 Fi gure 6. Magna Earthquake Sequence https://quake.utah.edu/ monitoring-research/2020-magna-earthquake-sequence Fi gure 7. Magna Earthquake Sequence https://quake.utah.edu/ monitoring-research/2020-magna-earthquake-sequence Continued from the previous page Three Salt Lake County schools had notable damage: Cyprus High in Magna, West Lake Junior High in West Valley, and Silver Crest Elementary in Herriman. The most significant damage at Cyprus High occurred near the swimming pool and the library. The school is being repaired for use until the opening of the replacement structures, estimated to be completed in 2024. 14 West Lake Junior High, the hardest-hit school building, is a concrete frame building with URM interior walls. Damage at the entry corridor is shown in Photograph 8. The school district is currently determining whether to repair or replace the structure. The International Existing Building Code 2018 (IEBC 2018) includes a disproportionate earthquake damage clause that can trigger a comprehensive seismic upgrade. This provision will probably be cited often in future moderate earthquakes along the Wasatch corridor. Damage to 10-year-old Silvercrest Elementary School, a more modern school, may indicate larger community problems in new construction. Silvercrest is approximately 18 miles from the epicenter of the Magna earthquake. Shaking from the earthquake was strong enough to cause masonry veneer debris to fall from archways directly over school entrances. Due to the nature of the school building’s damage, it is reasonable to conclude that injuries would have occurred if the school had been in session that morning. Health care facilities were largely unaffected by the earthquake, although certain older health centers were temporarily closed for building evaluations. The Utah Coronavirus hotline was shut down due to an evacuation of the call center building. The state public health office stopped processing COVID tests but resumed in less than 24 hours. 15 Infrastructure impacts were largely limited to power outages from the blown transformers. By 8:08 a.m. the morning of the earthquake, Rocky Mountain Power reported 55,000 customers without power. Service was reportedly restored to all customers after midnight. Due to the unprecedented circumstances of the ongoing pandemic, earthquake recovery is occurring largely in the background. Another disaster was declared as Salt Lake County suffered more damage in neighborhoods from downed aging trees and power lines when hurricane-force winds accompanied a storm in September. The damage from the Magna earthquake sequence, a moderate event, was significant. Dr. Keith Koper of the University of Utah Seismograph Station noted that the largest earthquake that experts determine could be generated from the Wasatch fault system is up to an M W 7.1. The energy released from an event of that size would be approximately 90 times Magna’s energy release. 16 The EERI Scenario document, published in 2015, delineates the damage due to an event of that magnitude in Salt Lake. 17 The HAZUS results are staggering. Updated economic losses have been revised upward to an estimated $52 billion since this document’s publication. State emergency managers will be recalibrating these models with information gathered in the Magna event. The disaster risk we face as a community has not gone unnoticed. The Utah Division of Emergency Management teamed up with FEMA Region VIII to hold a two-day summit on unreinforced masonry buildings in Utah in June 2019. 18 This gathering of experts, government officials, and community organizations highlighted the needs of our community. The summit led to a large collaborative effort to generate the Wasatch Front URM Risk Reduction Strategy — a program intended to implement the federal National Mitigation Investment Strategy (NMIS), with goals to invest in ways that benefit the whole community. The final strategy document, published on the Magna quake’s anniversary, presents ideas to meet three goals: 1) show how mitigation investments reduce risks, 2) coordinate mitigation investments to reduce risks, and 3) make mitigation investment standard practice. FEMA Region VII has identified the Wasatch Fault as “one of the most probable catastrophic natural threat scenarios in the U.S.,” noting that experts project that a major earthquake on the Wasatch Fault would be among the deadliest disasters in U.S. history. A national-scale FEMA