Faults May Give Clues to Next Quake
A group of scientists has a theory: Suppose the major faults along the coast between Los Angeles and Ensenada are all connected. And suppose that over the last several hundred years, there have been a series of quakes along various segments, moving steadily northward.
If this is true, the destructive 1933 Long Beach quake on the Newport-Inglewood fault would be just the latest in a sequence of temblors, with the next one slated to occur along the fault line between Compton and Beverly Hills.
Such a quake could be devastating because it would take place in one of the most densely populated areas of Southern California. The magnitude 6.4 Long Beach quake hit before the area was heavily populated, yet it killed 120 people.
Two geology professors, doing their research under the auspices of the Southern California Earthquake Center, offer this thesis in a publication called Seismological Research Letters. This journal gives researchers freer rein than other scientific publications to speculate on theories that have not been completely proven.
Lisa B. Grant of UC Irvine and Thomas K. Rockwell of San Diego State acknowledge that their thesis is being fine-tuned. One reason is because some of the faults cannot be precisely studied in terms of the timing of past earthquakes because they are under the ocean. Several of the quakes they write about predate the establishment of the Spanish missions and historical records. As a result, their dates are uncertain, based on radiocarbon dating found in sediments and accurate only within 125 years or so.
"We made it clear it was speculative," Rockwell said in an interview. "But every place we studied has produced an earthquake in the past few hundred years. What we don't know is when the northern part of the Newport-Inglewood last ruptured."
Caltech seismologist Egill Hauksson calls the work by Grant and Rockwell "bold," even though he may agree with their caveats.
"Bold" is a word scientists sometimes use when they talk about basing a thesis on uncertain facts. But Hauksson himself joined in published speculation last year that fits into the theory. His article said that two moderate magnitude 4 quakes near Beverly Hills in 2001 could be precursors of a larger quake on the northern segment of the Newport-Inglewood fault.
