After 1,000-Quake Day, Shaking at Mammoth Declines

In the ebb and flow of this eastern Sierra ski resort’s five-month-long volcanic earthquake swarm, Sunday was a day of ebb.

After more than 1,000 earthquakes over a 30-hour period beginning about 4 a.m. Saturday--including three in the 4 magnitude range and 28 in the 3 range--the number of quakes by Sunday afternoon had dropped to about seven an hour, all of them below magnitude 3.0.

Mammoth residents and officials interviewed Sunday said that for the most part they were not too bothered by Saturday’s surge of quakes, although some said they were worried.

U.S. Geological Survey scientists monitoring volcanic precursors in the area expressed relief. They issued a statement noting that Saturday’s seismic activity “began to approach some of the guidelines” for declaring a yellow volcanic alert, which would have entailed setting up an emergency field station at Mammoth and declaring the area one of intense volcanic unrest.

But because of the waning of the quakes, the statement said, Mammoth Lakes remains in a no-immediate-risk “green” status, where it has been during the months-long swarm up to now.

Wally Hofmann, the publisher of the local weekly newspaper Mammoth Times, in a message on the paper’s World Wide Web site Sunday morning, made light of Saturday’s temblors.

“Yes, we have been a little shaken up with the earthquakes, but nothing to fear, we are still . . . pretty much normal,” Hofmann wrote. “Where else can one experience the thrill of an earthquake without getting hurt?

“I think we have a new tourist attraction,” he said. “Really, truly no one has been killed or even injured from a Mammoth-area earthquake since they’ve been keeping track 100 years ago. Can Los Angeles or San Francisco say that?”

But Hofmann acknowledged that a graphic designer he knew had become so concerned by the quakes Saturday that she left town to stay with relatives in Virginia City, Nevada, near Reno, for a couple of days.

At the Mammoth Mountain Ski Area, marketing director Pam Murphy said that when the largest of Saturday’s jolts, the 4.8 quake, occurred at 9:20 a.m, ski lifts were briefly closed to check for any damage. She said none was found. The ski area is a few miles west of town, and the quakes have been centered two or three miles east of it, so the area did not get the full effect of the shaking.

Some among the about 2,000 early season skiers this weekend had questions about the quakes, she said. Those who were most concerned were allowed to use the resort’s Internet to find out what the geological survey scientists were reporting, she said.

Sunday was a cool, sunny and placid day. But 12-year-old Norma Sanchez, a student at Mammoth Middle School, said she had been “scared, not knowing what was going to happen” from Saturday’s quakes.

The geological survey, meanwhile, issued a statement on the “long-term outlook for volcanic activity” in the Mammoth area and noted:

“All but three of the 20 or so eruptions over the last 5,000 years have been explosive in nature, [but] all have been small to moderate in scale.”

The statement added that intense volcanic unrest at levels that were approached but not quite reached Saturday “can temporarily increase the odds that an eruption can follow. The U.S. Geological Survey’s monitoring program is designed to recognize the sort of unrest that indicates a significant increase in the chances of an imminent eruption.”