M_W4.9 Yucaipa Earthquake of June 16, 2005

and the M_L4.0 Aftershock of June 27, 2005

California integrated Seismic Network/ Southern California Seismic Network

The M4.9 Yucaipa event occurred on an almost east-west striking vertical fault with thrust motion and a small left-lateral strike-slip component. It is consistent with uplift of topographic features in the area, such as the Crafton Hills. The M4.0 earthquake is within the aftershock area of the M4.9 event. The M4.0 event is located only about 1.0 km to the west of the M4.9 hypocenter and about 1.0 km shallower. It exhibited strike-slip motion, most likely on the left-lateral plane or the plane striking at a high angle to the direction of the San Andreas fault. In detail, the aftershocks form two subparallel clusters that trend almost east-west and are offset by a few hundred meters. This latest M4.0 aftershock is probably associated with the westernmost cluster.

To view the SCSN Special Report for this event, click here.

Also see: www.cisn.org

M_w5.2 Anza Earthquake of June 12, 2005

There was a M_W5.2 earthquake at 8:41AM PDT, located 6 miles ESE of the town of Anza, CA. The event was felt throughout the southern portion of California, and as far away as Nevada, Arizona, and Baja California. The strongest shaking may be seen by viewing the ShakeMap below. To view the full-size ShakeMap for this event, click here.The SCSN Special Report may be found by clicking here .If you felt this earthquake, and would like to report it, click here.

If you have questions or concerns regarding the magnitude change from the originally reported M_L5.6 to the current M_W5.2, Dr. Kate Hutton has written an explanation that may help the public and media understand the difference between the two reported magnitudes. To access the article, go to the News/Updates section of the SCSN site by clicking here.

AFTERSHOCK PROBABILITY REPORT

STRONG AFTERSHOCKS (Magnitude 5 and larger) - At this time (immediately after the mainshock) the probability of a strong and possibly damaging aftershock IN THE NEXT 7 DAYS is approximately 20 PERCENT.
EARTHQUAKES LARGER THAN THE MAINSHOCK - Most likely, the recent mainshock will be the largest in the sequence. However, there is a small chance (APPROXIMATELY 5 TO 10 PERCENT) of an earthquake equal to or larger than this mainshock in the next 7 days.
WEAK AFTERSHOCKS (Magnitude 3 to 5) - In addition, approximately 5 to 25 SMALL AFTERSHOCKS are expected in the same 7-DAY PERIOD and may be felt locally.

This probability report is based on the statistics of aftershocks typical for California. This is not an exact prediction, but only a rough guide to expected aftershock activity. This probability report may be revised as more information becomes available.

To view the entire Aftershock Probability Report, click here.