Coincidentaly, there was a News Release this morning about the time of the quake:

Catherine Puckett
USGS, Western Region
Office of Communications
371 Redmond Rd.
Eureka, CA 95503

News Release Address:
U.S. Department of the Interior 4200 University Dr.
U.S. Geological Survey Anchorage, Alaska 99508

For Release: Contact:

October 23, 2002 Peter Haeussler Catherine Puckett

USGS Study Shows that Anchorage Area Fault May Be Due for Large Quake

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. The study, which examined the ancient
earthquake history of the Castle Mountain fault, was just published in the
October issue of the Geological Society of America Bulletin.

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. Therefore, he
said, a magnitude 6 to 7 earthquake may occur on this fault in the next 50
to 100 years.

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, respectively. The Castle Mountain fault is part of a larger field of
folds and faults in the Cook Inlet region that are capable of producing
magnitude 6-7 earthquakes, but because geologists consider the Castle
Mountain fault one of the largest and most significant in the region,
understanding its earthquake history is important.

To evaluate the earthquake history of the Castle Mountain fault,
researchers dug trenches up to 6 feet deep and 100 feet long across the
trace of the fault west of Houston, Alaska. The scientists carefully mapped
the walls of the trenches, analyzed the relationships between geologic and
soil units, and collected samples for radiocarbon dating.

Haeussler and his colleagues found that the fault was not a simple zone
where the different geologic sediments were cleanly offset, but rather, "it
was a zone of goo" where sediments liquefied and flowed during ancient
earthquakes. Unlike similar studies in the lower 48 states, the dense root
mat that covers the fault acted like a strong blanket and did not break
during ancient earthquakes. As a result, said Haeussler, it was much harder
to precisely specify the timing of ancient earthquake events. Also, because
the sediments were near the surface and they flowed, the ancient
earthquakes must have occurred in the summer months because the sediment
was not frozen and able to flow.

The 1964 magnitude 9.2 earthquake that occurred in southern Alaska was
related to a slip of the Pacific plate beneath southern Alaska. In
contrast, said Haeussler, earthquakes that occur on shallow geologic
structures, such as the Castle Mountain fault and the related field of
structures in Cook Inlet, may not produce great earthquakes, but they are
closer to where people live and work, and as a result may have more impact
when they occur. Consequently, this new study of the ancient earthquake
history of the Castle Mountain fault greatly increases the understanding of
a particular type of earthquake hazard, but ideally there should be studies
on all the structures in Cook Inlet to better evaluate how quickly they
move, how large are the earthquakes they produce, and how often they occur.

The abstract of this paper, "Paleoseismology at high latitudes: Seismic
disturbance of upper Quaternary deposits along the Castle Mountain Fault
near Houston, Alaska," can be found at
http://www.gsajournals.org/gsaonline/?request=get-abstract&issn=0016-7606&volume=114&issue=10&page=1296

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