June 13, 07:00 PDT:
The magnitude of the earthquake was revised from its preliminary estimate
of ML5.6 to Mw5.2.
June 12, 14:00 PDT:
A local magnitude M5.2 earthquake occurred 9 km (6 miles)
east-southeast of Anza, California at 8:41 am on Sunday, 12th of June
2005. The mainshock focal depth was 13 km (8 miles). The earthquake
is located within the San
Jacinto fault zone and within the
Anza "gap" (where future M>6 events are expected). The earthquake
was widely felt across all of southern California and into Nevada
and Arizona. The strongest shaking occurred to the northwest of
Anza, about 25 km (15 miles) to the south of Palm Springs.
The earthquake probably occurred on a small "cross fault" within the
San Jacinto system. A "cross fault" is a small fault at a high angle
to the main fault, that accomplishes the same overall strain.
The San Jacinto fault strikes northwest with right-lateral
strike-slip motion, while the alignment of aftershocks to the M5.2 suggests a
northeast strike to its fault. The depth of the earthquake is 13 km.
This depth puts the earthquake below the section of the fault
thought to be accumulating slip for a large future earthquake.
The San Jacinto fault is a 200 km long branch of the San Andreas
system that accommodates horizontal motion between the North
America and Pacific Plates. The past history of the region
includes numerous M5 events, including
a M5.1 on 31st of October 2001 and a M6.0 earthquake
that occurred in 1937, located about 10 miles to the southeast of
The San Jacinto fault is the most active earthquake fault in
California, producing an earthquake of at least 6 eight times
in the last century, including:
Egill Hauksson and Lucy Jones