16 February 2016 | Quake Insights
The M=4.8 Big Pine, CA quake was followed by a M=4.2 aftershock and several smaller ones; both are right-lateral ruptures at a depth of about 15 km (9 mi). They struck in a very active belt of the ‘Walker Lane’ active faults and volcanic features.
The 1872 M=7.6 Owens Valley earthquake is the third largest shock to strike California since reliable accounts began in about 1800, exceeded only by the 1857 M=7.9 and 1906 M=7.7 shocks on the southern and northern San Andreas faults respectively. Although the magnitudes of pre-instrumental quakes are uncertain, the surface slip and rupture length was carefully mapped by Lubetkin (1988) and Beanland and Clark (1994), and so only it’s depth extent is uncertain. As a result, few doubt that this was the third largest California quake.
Right-lateral slip on the Owens Valley fault during the past 20,000 years is 1-4 mm/yr, according to Beanland and Clark, 1994 and Lubetkin, 1988, or about a tenth of that on the San Andreas. So great shocks on the fault must be much less frequent, but no less damaging, than on the San Andreas. The 1872 earthquake produced right-lateral offsets averaging about 6 m (20 ft) along the 100 km fault length, according to Beanland and Clark (1994).
The great John Muir, founder of the Sierra Club, and champion and defender of Yosemite, was camped in Yosemite Valley at the time of the 1872 quake, and witnessed massive rockfalls in response to the shaking. Beautifully capturing the excitement we all feel when the earth reveals her dynamism to us, he wrote in his journal,
“…though I had never before enjoyed a storm of this sort, the strange, wild thrilling motion and rumbling could not be mistaken, and I ran out of my cabin, near the Sentinel Rock, both glad and frightened, shouting, ‘A noble earthquake!’ feeling sure I was going to learn something. The shocks were so violent and varied, and succeeded one another so closely, one had to balance in walking as if on the deck of a ship among the waves, and it seemed impossible the high cliffs should escape being shattered.”
Ross Stein and Volkan Sevilgen
Data from USGS, California Geological Survey; Sarah Beanland and Malcolm Clark (1994), The Owens Valley fault zone, eastern California, and surface rupture associated with the 1872 earthquake, U.S. Geol. Surv. Bull., 1982, 1–29; Lester Lubetkin (1988), Late Quaternary activity along the Lone Pine Fault, eastern California, Geol. Soc. Am. Bull., 100, 755–766; Steven G. Wesnousky (2005), Active Tectonics of the Walker Lane, Tectonics, 24, doi:10.1029/2004TC001645.
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