Grant, L.B. & Rockwell, T.K.
A Northward Propagating
Earthquake Sequence in Coastal Southern California?
Poster presented at Southern California
Earthquake Center Annual Conference 2002 in Oxnard, California.
Fault investigations in the northern Baja
California peninsula (Mexico) and coastal southern California (USA) reveal
evidence for geologically contemporaneous or sequential earthquakes along a
300-km-length seismic zone including structures previously mapped as the Agua
Blanca, Rose Canyon, San Joaquin Hills and southern Newport-Inglewood fault
zones. Radiocarbon dating and the historic record indicate that moderate to
large earthquakes occurred after 1640 +/- 160 A.D., 1523 to 1769 A.D., and 1635
to 1855 A.D. on the Agua Blanca fault, Rose Canyon fault and in the San Joaquin
Hills, respectively. A M(w) 6.4 earthquake on the southern Newport-Inglewood
fault zone followed in 1933 and increased the Coulomb stress on the northern
Newport-Inglewood fault zone in Los Angeles. An energetic sequence of moderate
magnitude earthquakes last year suggest the possibility that the northern
Newport-Inglewood fault zone is close to failure and may culminate a
multi-century northward propagating sequence of earthquakes.