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Some 900,000 Utahns are preparing to take part in the state's largest earthquake drill Tuesday morning, dubbed the Great Shake Out.

Schools, businesses, hospitals and government agencies are participating in the mock quake, slated to begin at 10:15 a.m., on a voluntary basis.

The drill is aimed to increase preparedness for a serious threat. According to the Utah Seismic Safety Commission, 90 percent of the state's population lives in earthquake zones. A seismic belt about 100 miles wide extends north to south along the Wasatch Front and through Richfield to Cedar City and St. George, according to the commission.

If a magnitude 7.5 quake were to occur in the Salt Lake City area, the commission predicts there would be some 7,600 deaths and $18 billion in physical damage, loss of jobs and economic activity.

The Great Shake Out website details strategies to stay safe during and after an earthquake. As a general guideline, the Shake Out encourages people who are indoors to drop to the ground, take cover by getting under a sturdy desk or table, and hold on to it until the shaking stops. —

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Send your Great Utah Shake Out photos to The Salt Lake Tribune by emailing with Shake Out in the subject line.

Follow along at as we curate reactions from the Web and live-tweet the event (#shakeout). —

Impact from a major quake

Injuries and deaths from a major quake

The number of injuries and deaths would depend on the time of day of the earthquake. The Utah Division of Homeland Security ran the scenario of a 7.0 temblor hitting Salt Lake County at a time when everyone is home, everyone is at work, and when people are commuting.

Level 1: scrapes and bruises

Level 2: hospitalization with non-life-threatening injuries

Level 3: life-threatening injuries

Level 4: fatalities

2 a.m.

Level 1: 31,430

Level 2: 9,360

Level 3: 1,480

Level 4: 2,920

2 p.m.

Level 1: 22,830

Level 2: 7,060

Level 3: 1,200

Level 4: 2,290

5 p.m.

Level 1: 23,520

Level 2: 7,790

Level 3: 2,290

Level 4: 2,450