4.2 Castaic earthquake, 20-plus aftershocks 'normal' seismic activity
A magnitude-4.25 earthquake struck about 9 miles north of Castaic Saturday evening. By Brenda Gazzar, Los Angeles Daily News
Posted: 01/04/15, 11:13 AM PST
A 4.2-magnitude earthquake that struck about eight miles north of Castaic on Saturday night and more than 20 aftershocks have not resulted in any reported damage or injuries in Los Angeles or Ventura counties, authorities said Sunday morning.
Shaking was widely felt in the San Fernando Valley and as far south as Long Beach during the earthquake at 7:18 p.m. Saturday, according to U.S. Geological Survey officials. The earthquake was preceded by a foreshock with a 3.0 magnitude at 6:58 p.m. and was followed by about 20 aftershocks, including a 2.5 magnitude one at 1 a.m. Sunday, said seismologist Lucy Jones, science advisor for risk reduction at the U.S. Geological Survey.
It's "an ordinary level" of seismic activity, Jones said. "Southern California last year had eight earthquakes of this size or larger. It's the size of earthquake we have once every month or two...This got felt by more people because it was closer to a lot of us. There were more people nearby so more people felt it."
There was a 4.2-magnitude quake in the sparsely populated Salton Sea area on Christmas Eve and "hardly anybody noticed it," she said, "so having people near it makes a difference."
While every earthquake has a 5 percent chance of being followed by an aftershock bigger than itself, that percentage had decreased to 1 or 2 percent by Sunday morning, she said.
Jones, who is Los Angeles Mayor Eric Garcetti's science advisor for seismic safety, worked on a far-reaching earthquake preparedness plan the mayor released last month, "Resilience by Design," that would require owners to retrofit their pre-1980 buildings and called for improved water and telecommunications systems.
While some of the recommendations can be carried out by executive action, others require ordinances to be approved by the City Council. Jones said she will explain these recommendations and answer any questions about them on Jan. 14. She expects things to move forward soon after that.
On buildings, the soft-sided construction used for most apartments will need to be retrofitted in five years at the owner's expense, which is estimated to be $5,000 per two-bedroom apartment. Among the things the council will consider is whether the current rent stabilization ordinance — in which owners have the right to pass costs of mandated upgrades to tenants with limited increases each year — should be followed and whether apartment owners should be required to pick up some of the costs themselves, Jones said.
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