Orange County Branch Newsletter
Branch News - May Joint Luncheon
May Joint Luncheon with APWA
Life on the Ring of Fire and Emergency Response
This month’s meeting on May 26th was held jointly with American Public Works Association (APWA) at their events location in Lakewood. It was the first joint event held by our two organizations and the mood was light as attendees looked forward to hearing about the event topic to be presented by experts from USGS and CalEMA. ASCE also took the opportunity to present the ASCE Achievement Award to this year’s recipient, Ms. Christine Truong of CSULB.
Moderated by Ms. Joyce Amerson of the City of Irvine, our guest speakers included Mr. Eric Pounders from the USGS and Mr. James Goltz, Ph.D. of CalEMA. Mr. Pounders began with his presentation covering the basics of plate tectonics for the west coast United States and the Pacific and included a general discussion of California earthquake faults with an emphasis on the Southern California fault system. He also described worldwide phenomena of continental drift as having movement at a rate similar to the “time it takes for fingernails to grow”.
Eric Pounders of USGS
Most of us know that California is situated on both the North American and Pacific Plates. As the North American plate moves north and west, stress builds up which sooner or later needs to be released; therefore, we have movement. In Southern California alone, there are approximately 300 faults. Mr. Pounders described to us the difference between the three main type faults including “strike slip”, “normal”, and “thrust”. The thrust fault is the type found in Chile and Japan where one side of the fault or one plate goes under the other.
We also learned that the USGS monitors seismic activity using GPS in real time through the seismometer. The instruments can now detect movements and send out an alert 30 seconds prior to what could be the strongest shaking of an event. There are over 200 GPS in the array of USGS equipment installed.
The earthquakes of 1857 (magnitude 7.0) and 1906 (magnitude 7.8) were the largest of record for California while the 1933 Long Beach quake resulted in a major revamping of the building codes at that time According to Mr. Pounders, a large magnitude earthquake is known to have occurred within every 150 to 300 years along the San Andreas Fault. So the next big quake along the southernmost end of the San Andreas could be around a 7.7 magnitude.
Mr. Goltz, Ph.D., Earthquake and Tsunami Program Manager, presented implications of the 9.0 magnitude Tohoku Japan Earthquake of March 11, 2011. Foreshocks were felt a day or two prior to the main earthquake where the Pacific Plate moved west beneath the North American Plate (and Japan) and generated a trans-Pacific tsunami. The quake was the largest to hit Japan in 1,200 years and rupturing the fault an area 330 km by 150 km. It is currently estimated that 97 percent of the casualties and damage resulting from the Tohoku Japan quake were actually due to the tsunami. Regretfully, there have been approximately 15,234 lives lost so far and another 8,616 are still considered missing.
Mr. James Goltz, Ph.D. of CalEMA
The secondary hazard, the radiation leaks at the Fukushima Nuclear Facility were and still are of great concern. Although the plant withstood the forces from the earthquake fairly well, the tsunami toppled over the sea wall resulting in damage to the pumps and where leaks in the tanks caused explosions due to overheating.
The tsunami notification protocol was enacted here in California as there was a real threat to certain areas along the coast including Crescent City and Santa Cruz. Fifteen coastal counties and another five along the San Francisco Bay were notified. The waves, over a period of 30 hours, came in cycles beginning at low tide. High tides later on caused damages due to dangerous current. One fatality was reported at the mouth of the Klamath River.
So just what is it that we have learned from other quakes and natural disasters including Japan? Although an abundance of data has been collected and continues to be studied, our presenters advised us “don’t underestimate your seismic risk… and don’t over-rely on technology”. In order to mitigate future tsunamis, major changes in land use planning may be the most effective. Additional information and recommendations for responding to an earthquake are included in the PowerPoint presentation below.
We hope to see you at our next luncheon event!
Get ready for the next “Big Shake” October 20, 2011 at 10:20AM!