The thread on "Realism on a California Earthquake" got me thinking about a comparison with the recent actual quake in Nepal.

Size of Quake

The Nepal quake of April 25, 2015 was a M 7.8, and was followed a day later with a M 6.7 aftershock.

This is roughly comparable to what might be expected for the "big one" on the southern San Andreas Fault. Indeed, the hypothetical earthquake the USGS envisioned for the ShakeOut Scenario was also an M 7.8.

Population Involved

Nepal's population is about 28 million. I can't find the reference at the moment, but I recall reading that the UN said about 6 million people were directly impacted by the Nepal quake.

Pete's estimate in the other thread was that there are about 13 million people in SoCal, and he assumed about half , or about 6.5 million people might be directly impacted. Recognizing that both these estimates are very approximate at best, it is clear that roughly comparable numbers of people might be directly effected.

Infrastructure and Preparedness

Nepal is a developing country, that until recently was in the midst of a civil war. The government was barely functional in the best of times. While some efforts had been made to prepare for earthquakes, most of the construction was not seismic resistant. Nepal is also a very rugged country, with few modern roads. Much of the country is only accessible by foot, even in normal times. There is only one modern airport at Kathmandu capable of landing large aircraft.

California is overall a very modern state. Recent building codes take earthquakes into account. While by no means all older structures have been seismically retrofitted, many have. In recent years CalTrans has made major efforts to retrofit existing bridges and other highway structures. While some areas in California are topographically rugged, most populated areas are nowhere near as difficult terrain as is Nepal. California has an excellent modern highway system and numerous fine airports.

Earthquake Casualties

The 2015 Nepal quake killed about 8,800 people and badly injured more than 23,000. Hundreds of thousands were made homeless, just prior to the start of the monsoon in June.

We don't know how many would die in SoCal, since the "big one" hasn't happened yet. The ShakeOut Scenario (page 201) estimated 1,800 deaths, 750 major injuries, and more than 50,000 minor injuries.

Emergency Response and Recovery

In spite of a rapid and world wide response, the effort in Nepal has been severely handicapped by the rugged terrain and minimal infrastructure. The fact that even in normal times the Kathmandu Valley has only one reliable road to India, and only one airport capable of handling large aircraft has made post earthquake support from outside very challenging. Much of the country is inaccessible except by foot or helicopter.

Even allowing for major disruptions due to earthquake damage, it would appear that SoCal would face a much less severe problem for getting help from the outside world. While terminals and hangers may be demolished, airstrips themselves generally don't get too severely damaged in earthquakes. And California has an abundance of fine airstrips. Likewise, while roads may be damaged, a bit of work with a D-9 Cat can quickly make a damaged road passable, at least for emergency convoys.

None of the above is to say that a major earthquake in Southern California wouldn't be a severe disaster. Many people would die. And it would be a long time before things returned to normal. But I think all things considered, California is much better prepared than Nepal was.

I agree with you on a number of important points. The estimate of deaths is probably pretty good for So Cal. Something in the region of 2000 dead, and 50,000 injured. I see the problem areas as being the "bedroom" communities that are located beside the San Andreas. Unfortunately, these so called-bedroom areas of LA are not just bedrooms any more. They have grown to become full-scale communities in their own right. So places like Palm Springs, Palm Desert, Indio, Beaumont, Redlands, San Bernadino, Hesperia, Palmdale ... all these towns have seen a large amount of building. And ironically, it means that large numbers of people are living within 5-10 miles of the San Andreas. And a surprising number of people are living, or having daily activities, right on top of it. It is madness really. But it is human nature - big quakes are so rare.

I absolutely agree that the USA is vastly better prepared than Nepal. I am confident that over the long term, the relief effort will be massive and much help will come to LA. As I wrote before, I am more concerned about the short-term psychological reaction of people in LA. And really, the major problem is that few of these people have followed the advisories and put enough water aside to last for a few weeks. That is really the main thing that people need to do to survive. One step!

I really like your idea of a Special Access Team with bulldozers. I think they might also need some bridge-building equipment to get over deep chasms in the ground. Organizations like the Army Corp of Engineers and the Navy SeaBees would be absolutely perfect for this. It would be tremendously helpful if Washington DC had a fast-response plan to mobilize these people.

For example, they just tell the Army Corp of Engineers ... "we want you to re-establish a new access road coming from the east, starting at Arizona (town of Quartzite) and going all the way to the heart of LA. Use existing roads as much as possible, clear all debris from your route, build bridges if you have to, and do what it takes to connect to downtown LA".

Likewise they tell the SeaBees ... "we want you to establish ONE new access road coming from the south, starting at Yuma, Arizona, and going all the way into LA. Use existing roads as much as possible, clear all debris from your route, build bridges if you have to, and do what it takes to connect to downtown LA".

That kind of activity would save a LOT of lives. But these teams would need to be mobilized very fast!! And they would need a lot of equipment to get the job done.

Probably the big unknown for LA is the potential of large-scale fires. It was a major problem for San Francisco during the 1906 quake. I think it will also be a major problem - and frightening - for some areas of LA. As residential values have shot up, many developers have built apartment blocks. High-density housing exists in many suburbs. And So Cal is very dry because of the long-term drought. So the fire risk is very real.

I have been watching what happened in Nepal. And to be perfectly honest, I was really wishing I could get over there to help people. They got some immediate aid within the first month. But I think the statistics say that they have only received something like 15-20% of the assistance they need to recover. I think that will be "typical" for global emergencies in the future.

Places like Katmandu (quake) and New Orleans (hurricane) teach us an important lesson. Sooner or later that "Big Disaster" really will come along. People talk about it, and they ignore it for a long time. But it does come eventually.

Pete

Agreed, potable water would be a huge issue. Especially from about day 2 until a week or so. Most households can probably find enough fluids to survive for 24 hours or so. After a week or two relief efforts will probably be able to spin up enough to deliver at least survival levels of water. It's the time in between that will be grim. Even in the Pacific NW potable water will be an issue after a Cascadia quake, but at least up there they have numerous natural water sources provided they have means to purify it. In the current drought SoCal is not so fortunate.

I think you nailed it. Fires could well lead to more fatalities than the actual quake itself. I seem to recall that during the flooding from Hurricane Sandy, a whole neighborhood burned to the ground. Not the usual risk one associates with floods, but it happened. SoCal is at orders of magnitude greater risk from fire after a quake.

A major earthquake in a heavily populated area will always be bad. Each region may have special issues which make it worse. In Nepal it was poor building codes, lack of transportation routes and rugged terrain. In SoCal it will likely be lack of water, and fires.

thanks. excellent discussion!
my practical take-away from this thread is the following:

1. I need to find my emergency radio, which has become "lost in the shuffle". I need to check the batteries.
2. I need to put away some spare gasoline. this is always a bit tricky, because it's a fire hazard. but it would be very useful to store some ... somewhere.
3. I need to keep augmenting my supply of water.
4. MOST importantly for me. I was thinking about the route to my house, in the event that LA has a major quake. I realized that my "exit route" crosses through a zone with a high fire hazard i.e. a suburb with very high-density houses, all located very close together. I need to cross that zone VERY quickly after the quake, before fires have a chance to become established. I will give some thought to this, and possible alternative routes.

Pete

OT: Earthquakes and broken terrain is one reason I have fought buying a road bike. I have an excellent Cro-Mo mountain bike with seriously good tires; something that can move quickly following an EQ but light enough that I can carry if the roads are really broken.

An MB should assist in crossing through areas with a high fire hazard... or were you thinking about driving?

I finally found a link to the big fire in NY during Hurricane Sandy: Battered Seaside Haven Recalls Its Trial by Fire . It makes sobering reading. Hope SoCal doesn't have quake during Santa Ana Winds!

Russ - yes I will be driving. it's OK, I've got a Jeep. but my strategy now is to park very close to the entrance to the parking lot (daytime) so I can get out easily, and quickly.

Pete