Monday, September 2, 2013

Latest rescue from Mussel Rock Park

The Daily Journal (San Mateo), Bay City News Service, 9/2/13.  "Coast Guard rescues injured hiker from cliff cave."

A hike around Mussel Rock in Pacifica
Mussel Rock Hillside trail, north end of Pacifica
"The U.S. Coast Guard helped rescue a person stranded in a cliff cave on the Daly City coast Sunday morning, according to the North County Fire Authority.

Nice view but not overnight after falling 100 feet
"Fire units responded to a report of a person who had fallen more than 100 feet down a cliff at Mussel Rock Park at about 4:40 a.m., according to the fire authority. 

....   The fallen victim was found inside a cave in the side of the cliff.  .... The victim was taken to a hospital with injuries that were considered serious, according to the fire authority."   Read article.

Related - Judging Earth by its cover blog, "Mussel Rock Beach Trail."  "Mussel Rock itself is a rock just offshore that has, you guess it, a lot of Mussels on it. It also attracts thousands of Sea Gulls. It’s not your average San Francisco white-washed rock, which was nice. According to geologists this area is the exact epicenter of the 1906 San Francisco earthquake. It marks the point where the San Andreas fault goes into the sea. It’s fairly obvious while hiking around the coastal rocks that something’s gone down in this area."  Note:  Muscle Rock Park photographs above and others may be viewed on the Judging Earth website. 

Posted by Kathy Meeh


Anonymous said...

The earthquake epicenter was in Marin County.

Fishermen would swim out to the rocks and fish.

If it happened at this time, he was either down there for a long time, or alcohol was involved.

Anonymous said...

Lomax (2005) determined probabilistic hypocentral locations for the foreshock and mainshock of the 1906 California earthquake through reanalysis of arrival-time observations in conjunction with modern wave-speed models and event location techniques. The Lomax (2005) “preferred” mainshock location has a large uncertainty volume (pdf), but is consistent with the association of initial rupture of the 1906 earthquake with an extensional right-bend (e.g. Lawson, 1908) or stepover (e.g. Zoback et al., 1999) in the submerged San Andreas Fault (SAF) system offshore of the Golden Gate.

Since the observed surface rupture for the 1906 earthquake occurred along the SAF (e.g. Lawson, 1908), we may assume that the focal region for the 1906 mainshock is located within the SAF zone. Then, an upper bound on a likely focal area is given by the intersection of: a) the SAF zone (as defined by the area between the SAF and the Golden Gate Fault in Bruns et al., 2002), b) the locations of recent micro-earthquakes in the area, and c) the uncertainty volume (pdf) for the Lomax (2005) “preferred” mainshock location. This area is bounded approximately by a polygon with corners at 37.79ºN-122.61ºW, 37.82ºN-122.57ºW, 37.71ºN-122.48ºW, 37.67ºN-122.53ºW, and center near 37.75ºN-122.55ºW (Figure showing 1906 focal area). This likely focal area extends northwestwards from offshore of Lake Merced to offshore of the southernmost Marin Peninsula. The southeast end of this area is a few kilometers to the northwest of the 1906 epicenter near Daly City of Bolt (1968), and near the proposed SAF stepover of Zoback et al. (1999).

We can constrain a likely focal volume, including depth, by assuming that the 1906 mainshock hypocenter is within or at the bottom of the seismogenic zone defined by recent micro-earthquakes, as has been found for a number of recent, large earthquakes on the San Andreas Fault system, e.g. Morgan Hill, 1984 (Cockerham and Eaton, 1984), Loma Prieta, 1989 (Dietz and Ellsworth, 1990), and Parkfield, 2004 (Langbein, et al., 2005). With this assumption, the depth range of recent micro-earthquakes in the likely focal area implies a 1906 focal depth between a few kilometers and about 13 km (Figure showing 1906 focal volume).