Earthquake in the Siskiyou Mountains
Stories from the heart of the
Siskiyou Mountains, Cave Junction, Oregon
One of the more notable disasters in Josephine County history hit
this region in 1873, a time when Illinois Valley was a major center
of commerce and Kerbyville was the county seat. Ironically, the
event is almost completely forgotten even though it is very likely
that it will happen again at any time and without warning. It always
pays to look back at history so we can be better prepared for
tomorrow.
The event took place on the evening of November 23rd, a time of
the year when residents in the region were probably preparing for
Thanksgiving as winter rain beat on the roof of their homes and snow
fell in the mountains. We can only imagine how startled they must
have been when one of the largest earthquakes in Oregon history
shook the mountains and communities of southwest Oregon and
northwest California.
Based on the damage and distance that the shockwaves that were
felt, the size of the quake is estimated to have been about
magnitude 7.3, almost the size of the quake that destroyed the city
of San Francisco in 1906. The epicenter of
the quake is estimated to have been near the southern tip of the
Kalmiopsis Wilderness, about 25 miles southwest of Cave Junction.
Damage from the quake was substantial.
All the chimneys were knocked down in the coastal communities of
Smith River valley and hardly a brick building in Crescent City
escaped damage. Chimneys were damaged in many places as far north as
Port Orford, Oregon, and east to Jacksonville, Oregon. Similar
damage was noted in the Illinois Valley communities of Waldo,
Browntown and Kerby. Travelers on the busy supply road between
Crescent City and Illinois Valley, reported large cracks in the
ground. Shaking was felt as far away as San Francisco and Portland.
Despite the potential danger of the event, there was no mention
human injury or death caused by the quake.
It is not surprising that earthquakes
occur in this region considering the geologic activity that is going
on about 20 miles below the Siskiyou Mountains. A massive slab of
ocean crust extending the entire length of Oregon is being pushed
slowly inland beneath us. As this massive slab of rock is pushed
deeper, it eventually melts and feeds the volcanoes of the Cascade
Mountains. Pieces of this ocean crust are scraped off under the
continent and, as these pieces accumulate, they push up the
mountains around us at a rate of about 1-2 millimeters a year.
Fortunately for residents in the heart of the Siskiyou Mountains,
the ocean crust heats up and becomes like warm taffy that be bent
and twisted because it is pliable rather than brittle. For this
reason, earthquakes are rare in this region. However, this is not
the case for the areas where the ocean crust is still cool and
brittle, such as along the coast. Earthquakes are common in the
coastal region, in fact small earthquakes of 1-2 on the Richter
Scale are happening all the time. Occasionally, larger earthquakes,
commonly in the range of magnitude 4-5, can be felt in coastal
cities. If an earthquake is large enough, there is a threat of a
tsunami hitting the coast, which explains why you see tsunami
warning signs along most of the Oregon scenic coast.
Story by Roger Brandt |
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