OC Area Fault Could Unleash 7.8 Magnitude Disaster

BY ALI SAHABI

The beauty of our Southern California landscape is also what makes it so menacing. We’ve long known the link between towering mountain ranges and the San Andreas fault. Now we learn that the coastal bluffs of Newport Coast and Laguna were created by another, potentially more deadly fault.

It was once thought that the Palos Verdes fault zone was a series of little faults, but Harvard researchers have determined it is one singular behemoth of a fissure capable of triggering a catastrophic 7.8 magnitude disaster. Published in the October Bulletin of the Seismological Society of America, the study explains how the twisting, dipping action of the fault has warped the coastline — creating the Palos Verdes Peninsula and other landmarks all the way to Dana Point.

If you thought the Northridge quake of 1994 was a whopper, you haven’t seen anything yet, seismologists warn. At a magnitude of 6.8, Northridge was relatively moderate, they say.

The U.S. Geological Survey recently estimated that a magnitude 7.8 earthquake in Southern California could cause the collapse of 50 brittle concrete buildings housing 7,500 people, and another five high-rise steel structures holding 5,000. From an economic standpoint, international modeling firm AIR Worldwide estimates losses from a quake of that magnitude at upwards of $300 billion. That figure was supported by data analytics firm CoreLogic, which said an earthquake of magnitude 8.3 along the San Andreas could damage up to 3.5 million homes, resulting in reconstruction costs of $289 billion.

Meanwhile, a 2020 study by the University of Southern California says the Puente Hills fault — running about 25 miles through the Los Angeles basin, from Downtown L.A. through La Mirada, and criss-crossing its way into Orange and San Bernardino counties — has the capacity to produce “the costliest disaster in U.S. history.” As many as 18,000 people would die, 735,000 would lose their homes, and up to 100,000 tons of debris would be generated. The total economic loss would be as high as $252 billion. That’s due mostly to its location: creeping underneath skyscrapers, heavily traveled infrastructure, and the bulk of the region’s more affordable — but also more vulnerable — housing stock.

What’s the difference between a 6.8 and 7.8 magnitude quake? The latter is 10 times larger in wave amplitude, and 32 times greater in release of energy — a difference equal to more than 54 million kilograms of TNT1 — more than twice the explosive power of the atomic bomb dropped on Nagasaki in World War II2. Even more startling, a 7.8 magnitude earthquake would unleash more than 1,000 times the energy of a 5.8 magnitude (32 x 32 = 1,024). A magnitude 9.0 quake or higher, which has happened five times since 19503 , releases more than a million times the energy of a 5.04 .

It’s important to understand the exponential nature of the numbers we assign to seismic events. Only then can we accurately assess the risks posed to our communities. Will your building survive the “Big One” when it comes? It could, but in many instances, a retrofit could significantly improve your odds.

Feel free to reach out to Optimum Seismic at 866 225-8450 or info@ OptimumSeismic.com for a complimentary consultation. We’ll help you

OC Area Fault — continued on page 32

1 United States Geological Survey, “Earthquake Magnitude, Energy Release, and Shaking Intensity,” https://www.usgs.gov/natural-hazards/earthquakehazards/science/earthquake-magnitude-energy-release-and-shaking-intensity?qt-science_center_objects=0#qt-science_center_objects 2 Wikipedia, TNT equivalent, https://en.wikipedia.org/wiki/TNT_equivalent 3 Wikipedia, Megathrust earthquakes, https://en.wikipedia.org/wiki/Megathrust_earthquake#:~:text=Megathrust%20earthquakes%20occur%20at%20 subduction,forms%20the%20contact%20between%20them.&text=Since%201900%2C%20all%20earthquakes%20of,greater%20have%20been%20 megathrust%20earthquakes. 4 Lumen, “Magnitude versus intensity,” https://courses.lumenlearning.com/geo/chapter/reading-magnitude-versus-intensity/#:~:text=The%20magnitude %20scale%20portrays%20energy,as%20a%20magnitude%205.0%20earthquake.