*REVISED* Notes from Battalion 4 CERT Meeting

William Selby gave a talk on Earquakes at the Battaion 4 CERT Community meeting last November. The following are from Battalion Coordinator Jim Stebinger.

NOTE: These revised notes contain four revisions suggested by Professor Selby. The revisions are asterisked.


*Revised Notes from Prof. William Selby's talk 11/16/06

Southern California is the junction of two large tectonic plates. “Our” plate is moving less than two inches a year.* The movement is not smooth and consistent, instead it is an average over time.

He presented a map that clearly shows the San Andreas fault and explained how scientists know we are overdue for a quake. A graduate student is credited with studying the fault and determining how it can be measured. Breaks, or shifts, leave telltale marks. The student figured out how to actually examine the fault and measure the signs of movement. His work was expanded and now it is clear that there is a major quake about every 150 years with a wide range of recurrence intervals ranging around 130-180 years.*. The last “Big One” was the Fort Tejon quake of 1857.

Therefore, we can expect a quake anytime that should be about 8.0 (plus or minus) on the seismic scales. Northridge was a 6.7. Therefore, this quake will be many times as powerful.

An 8.0 appears to be about the theoretical limit because we are not located at a subduction zone (where one plate goes under another). That is why the 1964 quake in Alaska was a 9.4, as it occurred at a subduction zone.

We are not close to meaningful prediction of quakes, although there is lots of study going on in that field.

The 8.0 will last about one minute. He is confident in our building codes and other legislation and feels that will save many lives. He estimates an 8.0 would kill around 300,000 people in less developed countries*. Here, he feels, the worst case scenario is up to 10,000 dead.

The death figures are highly variable. A quake when people are on the freeways, on the roads and at work will probably be more devastating than one that happens during off peak hours. He agrees that it is far more dangerous to be outside than inside. Fatalities will be directly connected to the number of people outside and below taller buildings, especially those who run outside of those taller buildings.*

How much damage will occur along faults other than the San Andreas is hard to predict. Epicenter, magnitude, time of day are the key factors. How much damage we will have in our immediate area is complicated by the numerous faults in our vicinity and how much they move, if at all.

Epicenter, magnitude, time of day are key.

Sadly, he feels the General public is completely unprepared. In his classes two or three per semester may have some kind of kit. He does not think the emergency preparedness effort has been well served by media. He is confident in our emergency services but very worried about what will happen to the general public.

He urged us to be prepared and constantly remind others. Most of the fatalities will be people outside of buildings, although some will die in collapses and other unusual circumstances.

He also discussed tsunamis and said he is “not losing sleep over a tsumami.” We should have plenty of warning from one across the Pacific and since it moves at the speed of an airliner we should have ample time to move to higher ground and the ground needn’t be too high. The Santa Monica bluffs, etc should be high enough. The more dangerous risk is one created by land movement off the coast (perhaps Catalina) which would eliminate the warning time. He was concerned that the recent quake in the Pacific did generate a six foot surge which evidently did not trigger a tsunami warning. He is hopeful that glitch will be fixed.

Finally, he discussed global warming and suggested that it will likely be a cause of weather related emergencies. He gave an overview of climate change. For a variety of reasons, some better understood than others, the global average temperature is warming and there are increasing numbers of “anomalous” weather events. Some parts of the issue are well-settled scientifically, such as the increase in temperature and the role of carbon dioxide, but still remain political footballs. Other parts of the questions are still subject to scientific debate.

In emergency preparedness terms, he said it would be prudent to expect extremes – higher high temperatures, lower lows, heavier rains and more powerful winds. Each of these events could trigger the need for CERT involvement. He said that extremely unusual weather patterns such as tornadoes (one or two small ones have hit our coast in recent times) and hurricanes* in Southern California are not impossible depending on how the global warming patterns play out.

Jim