3.0 Aftershock, Part of a Series, Rattles Area

The most recent of 13 quakes of at least magnitude 3--occurring during what has probably been a Northridge aftershock spasm--hit at 6:20 p.m. Sunday, when a 3.0 shaker rattled the epicentral area west of the Santa Clarita Valley.

Of Monday’s quakes, the strongest by evening was only a 2.4, about 500 times smaller than the 5.0 and 4.9 quakes that rocked the area early Saturday and Sunday.

But presuming that the latest sequence is not over, the Jet Propulsion Laboratory moved one of its global positioning instruments from Santa Barbara County to Granada Hills and said it would install another near Castaic.

“What we’re trying to find out is basically how the Earth’s crust is made up and how does it behave,” said the JPL’s Andrea Donnellan.

“We’ve been getting data since Northridge [on Jan. 17, 1994], and these aftershocks complicate the picture. We’re trying to find out if the strain in the Ventura Basin [extending from Magic Mountain through Ventura] has increased.”

Meanwhile, several scientists said that better knowledge of what fault was involved in the latest temblors must await a more precise calculation of where and at what depth the quakes occurred.