Earthquake involving Los Angeles’ Puente Hills fault could mean serious casualties and property damage

Previously: Seismic retrofits may be required for hundreds of apartment buildings in Los Angeles, Los Angeles: More than 1,000 concrete buildings at risk, nothing to be done, and Remembering Northridge: Thoughts on “Soft Story” Buildings

The Puente Hills fault system runs east of downtown L.A., straddling the 10 freeway towards the Inland Empire region. While California is known for its earthquakes, the Puente Hills fault system presents some serious concerns for seismologists.

These concerns were brought to the forefront during a recent earthquake centered in La Habra on March 28, 2014. The 5.1 quake sent powerful seismic energy towards the downtown area. While there was no major damage during that quake, scientists say that even a quake measuring just 7.5 on the Richter scale would have a devastating impact:

According to estimates by the USGS and Southern California Earthquake Center, a massive quake on the Puente Hills fault could kill from 3,000 to 18,000 people and cause up to $250 billion in damage. Under this worst-case scenario, people in as many as three-quarters of a million households would be left homeless.

One reason for the dire forecast is that both downtown L.A. and Hollywood are packed with old, vulnerable buildings, including those made of concrete, Jones said.

The violent motion would be amplified by the soft soil underneath the Los Angeles Basin and the valleys, which produces a jello effect as shaking waves wobble off the basin.

Source: LA Times

Below is a visualization of the Puente Hills fault produced by the USGS and the Southern California Earthquake Center:

Image of Peak ground velocity (PGV) map for a postulated magnitude 7.4 earthquake on Puente Hills fault in Los Angeles, California courtesy SCEC