More Quakes Rattle Mammoth

Some shallow volcanic earthquakes, including a few centered within a mile of the surface, were reported Monday in the Mammoth Lakes area after the latest surge in the ongoing quake swarm just east of town.

Virtually all the shallow earthquakes were much smaller than the magnitude 4.8 temblor and four quakes in the magnitude 3 range that struck Sunday afternoon, said chief Mammoth monitor David Hill of the U.S. Geological Survey.

Hill said it is too early to determine if there is a trend of shallow quakes. Hill noted that the Geological Survey still believes molten rock has reached no higher than about five miles beneath the surface, where it has been lodged for a long time.

More than 300 earthquakes were reported Monday, mostly centered about two miles east of Mammoth Lakes. This was nearly twice the number reported in the average day since the swarm began in late June.