Geologists just back from a reconnaissance of the 7.9-magnitude Alaska earthquake of November 3 confirm that rupture of the Denali fault was the principal cause of the quake. According to Caltech geology professor Kerry Sieh, Central Washington University geological sciences professor Charles Rubin, and Peter Haeussler of the U.S. Geological Survey, investigations over a week-long period revealed three large ruptures with a total length of about 320 kilometers. The principal rupture was a 210-kilometer-long section of the Denali fault, with horizontal shifts of up to nearly 9 meters (26 feet). This places the rupture in the same class as those that produced the San Andreas fault’s two historical great earthquakes in 1906 and 1857. These three ruptures are the largest such events in the Western Hemisphere in at least the past 150 years.
A new study by the U.S. Geological Survey (USGS) shows that the Castle Mountain fault in south-central Alaska may be ready to produce a strong magnitude 6 to 7 earthquake. Peter Haeussler, the principal investigator in the study, said his research demonstrated that major earthquakes occurred on this fault on average every 700 years or so in the last 2,700 years, and that the last significant earthquake along the fault occurred about 650 years ago. The Castle Mountain fault is the only active fault that comes to the earth’s surface in the Anchorage region, and the eastern part of the fault produced light to moderate magnitude 5.7 and 4.6 earthquakes in 1983 and 1996.
Mauna Loa,? Hawaii’s biggest and potentially most destructive volcano,? is showing signs of life again nearly two decades after its last eruption. Recent geophysical data collected on the surface of the 13,500-foot volcano revealed that Mauna Loa’s summit caldera has begun to swell and stretch at a rate of 2 to 2.5 inches a year, according to scientists from the U.S. Geological Survey and Stanford University. Surface inflation can be a precursor of a volcanic eruption, the scientists warn.