Baja, Mexico Earthquake
Felt by ~20 million people in Mexico and Southwestern U.S.
The northern Baja Peninsula of Mexico and areas of Southern California and Arizona were jolted by a 7.2 magnitude earthquake on Sunday. Two deaths and more than 100 injuries have been reported to date.
- Power and communication systems were down and structures were damaged in Mexicali (population 597,000).
- No major damage is currently reported from the Los Angeles or San Diego metropolitan areas.
- Interstate 8 in Imperial Valley has sustained some damage.
- Calexico reports ruptured gas lines with some residential fires and power outages.
- Selected cities north of the border that experienced shaking of varying degrees included:
- El Centro 38,000
- Calexico 36,000
- Imperial 10,000
- Brawley 22,000
- Escondido 137,000
- Chula Vista 213,000
As referenced in today's Claims Journal on-line, damage estimates from Sunday's earthquake are not expected to exceed $1 billion, and insured losses should not exceed $300 million, according to risk modeling firm EQECAT. While further damage assessment is still underway, Exponent would like to provide you with some background information that we have obtained and may keep you informed as to on-going events and damage to the local communities that you or your clients might be interested in knowing.
Observations from the damage reports to date?
- Maximum shaking intensity in Mexico was an VIII to IX – generally capable of causing moderate to heavy damage. Earthquake shaking intensity qualitatively measures the strength of shaking produced by the earthquake at a certain location. Magnitude measures the energy released at the source of the earthquake.
- Maximum shaking intensity in the U.S. was a VII – generally capable of causing moderate damage.
- Building inventory in the affected areas consists of structures that are a mix of vulnerable and earthquake resistant construction. Therefore, the damage to structures is expected to vary with vulnerability and proximity to the epicenter. The strongest shaking was recorded in Mexico where preliminary damage assessments have shown dramatic, and apparently isolated, building collapses. Preliminary damage assessments for the U.S. (areas further from the epicenter and less intense shaking) have indicated less severe damage.
What fault was responsible?
- The earthquake may have occurred along the Laguna Salada fault, although confirmation from on the ground is still needed.
- The earthquake resulted from the rupture of a 50 mile long section of a fault sliding laterally. (Baja moved northwest and the remainder of the North American continent moved southeast).
- Rupture of the fault began near Guadalupe Victoria in Mexico but "unzipped" along the fault to the north; this "directional effect" caused shaking to be felt more strongly north of the epicenter (e.g., towards Los Angeles) than in other directions at equal distances from the fault.
http://twitpic.com/1das3m
Where to Go for Additional Information
One of the best sources for information on the earthquake can be found at the USGS website.
For information on Exponent’s earthquake engineering services, please contact:
John D. Osteraas, Ph.D., P.E.
Group Vice President and Principal Engineer
Jon Wren, Ph.D., P.E.
Principal Engineer and Practice Director
Brian M. McDonald, Ph.D., S.E.
Principal Engineer and Practice Director
Exponent’s 24/7 Emergency Response: 888.656.3976 |
