Tectonic Alert is an SMS alerting system for earthquakes and volcanos in the United States. Text SHEEBA to (844) 571-2169 to subscribe!
The alert threshold is:
- 6.5+ magnitude earthquake in the continental U.S.
- 7.0+ magnitude earthquake in Alaska or Hawaii.
- Any volcanic eruption with hazardous activity both on the ground and in the air.
- 2.5 or less - Usually not felt, but can be recorded by seismograph.
- 2.5 to 5.4 - Often felt, but only causes minor damage.
- 5.5 to 6.0 - Slight damage to buildings and other structures.
- 6.1 to 6.9 - May cause a lot of damage in very populated areas.
- 7.0 to 7.9 - Major earthquake. Serious damage.
- 8.0 or greater - Great earthquake. Can totally destroy communities near the epicenter.
The southern San Andreas Fault is in a seismic drought. An earthquake has historically occurred every 180 years, give or take 40 years. The last earthquake happened around 1700, making this a catastrophe that's locked and loaded.
According to The ShakeOut Scenario, a 7.8 earthquake hitting along the southern San Andreas fault on a non-windy day at about 9 a.m. will unfold, approximately, like this:
- 1,800 people will die.
- 1,600 fires will ignite and most of those will be large fires.
- 750 people will be trapped inside buildings with complete collapse.
- 270,000 people will be immediately displaced from their homes.
- 50,000 people will need ER care.
- Search and rescue efforts will last for 19 days.
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The Hayward Fault lies to the east of San Francisco, across the San Francisco Bay. The distance between downtown San Francisco and the closest points of the fault in the East Bay is roughly 10-15 miles. Years between major earthquakes on the Hayward Fault: 158, 154, 96, 143. We're at 155. Yet another imminent California earthquake.
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What's especially terrifying about a San Francisco earthquake is that most of the city is at high risk of liquefaction. Liquefaction takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking. “Ten percent of buildings will collapse,” said Lucy Jones, the former leader of natural hazards research at the United States Geological Survey who is leading a campaign to make building codes in California stronger. “I don’t understand why that’s acceptable.”
Under pressure from oceanic plate Juan de Fuca, the stuck edge of North America is bulging upward and compressing eastward at the rate of millimetres a year. But it cannot do so indefinitely. There is a backstop—the craton, that ancient unbudgeable mass at the center of the continent—and, sooner or later, North America will rebound like a spring. If only the southern part of the Cascadia subduction zone gives way, the magnitude of the resulting quake will be somewhere between 8.0 and 8.6. If the entire zone gives way at once, an event that seismologists call a full-margin rupture, the magnitude will be somewhere between 8.7 and 9.2. Seismotologists have dubbed this The Really Big One 1
By the time the shaking has ceased and the tsunami has receded, the Northwest coast of the United States will be unrecognizable. The area of impact will cover some 140,000 square miles, including Seattle, Tacoma, Portland, Eugene, Salem (the capital city of Oregon), Olympia (the capital of Washington), and some 7 million people. Kenneth Murphy, who directs fema’s Region X, the division responsible for Oregon, Washington, Idaho, and Alaska, says, "Our operating assumption is that everything west of Interstate 5 will be toast."
The Pacific Northwest has experienced 41 subduction-zone earthquakes in the past 10,000 years. If you divide 10,000 by 41, you get 243, which is Cascadia’s recurrence interval: the average amount of time that elapses between earthquakes. Counting from the earthquake of 1700, we are now 315 years into a 243-year cycle.
The Aleutian Trench has more seismic activity than anywhere in the United States. It is responsible for the 9.2 magnitude earthquake near Anchorage, Alaska in 1964, which is known to be the most powerful earthquake ever recorded in North America, and the second most powerful earthquake ever recorded in the world. The entire trench is purposely not being monitored, as the Aleutian island chain is sparsely populated. Anchorage, however, is Alaska's most populous city and at highest risk for catastrophic damage. The 1964 earthquake killed 131 people and caused $3 billion of damage (in 2022 USD).
The highest earthquake risk in the United States outside the West Coast is in the New Madrid Seismic Zone. Damaging earthquakes are not as frequent as in California. But when they do occur, the destruction covers more than 20 times the area due to the geologic differences between the two regions. The USGS reports that catastrophic earthquakes visit the New Madrid region every 500-600 years, with the last one being in the early 1800s.
