Earthquake swarm near Salton Sea - is a big 'un coming?

[newbury]

Heard on the radio this a.m. and one official guy was saying they may be expecting a 7.3 to 7.9 "soon".

My question is - If an official says it might be 7.9 how close do they try to predict the size? Do they "underpredict" to not cause panic?

A quick check shows the biggest southern California earthquake ever recorded was a 7.9.

Beachfront property in Bakersfield?

 

[mostly_gas]

New Madrid fault in Missouri is "overdue". "They" expect a significant event because New Madrid has either small tremors or large movement. It is my understanding that any forecast is based on history rather than understanding of what is involved in platonic movement.

 

[orezok]

FINALLY! I get my ocean view :cool2:

 

[flusher]

Scary stuff for the So Cal folks.
My DILs childhood home is in the north San Bernardino suburbs and sits about 2 blocks from the San Andreas.

 

[Rock knocker]

Heard on the radio this a.m. and one official guy was saying they may be expecting a 7.3 to 7.9 "soon".

My question is - If an official says it might be 7.9 how close do they try to predict the size? Do they "underpredict" to not cause panic?

I think the 7.8 number came from a 2008 study of potential movement in that area. In any case, movements in the geologic past could be assessed and historical records of shaking could be looked at. If you had reports of earth shaking throughout an area on a certain day, you can make a good evaluation of what the shaking must have initially been based on the size of the area.

The offset of fault scarps can also be looked at, a larger physical offset causes a alrger earthquake. Baring a exposed fault scarp, you can look at other evidence of movement. That is what they did looking at flooded forests of the Washington coast. Based on C14 data, they know a huge area of coastal Washington subsided at the same time. A good guess can be made on how much subsidence occurred to flood the area with salt water, and the the numbers can be spit out. In the case of the Cascadia earthquake, they are now day certain that the quake occurred on January 27, 1700 because of historical records in Japan.

The near epicenter of the 1872 North Cascades fault is now likely known by the excavation of a fault near Entiat. Amoung the evidence looked at to estimate ground motion was that Omak Rock remained standing about 100 miles away.

Giant Washington Quake: It's Entiat's Fault | KNKX

 

[Rock knocker]

And to answer another question.

A good scientist would let his numbers stand as they are and not under estimate for the sake of any politics.

 

[orezok]

The 1992 Landers earthquake, 7.3 Ricter, was near me and had a maximum offset of about 19'. Given that, exactly where are my property corners now?

 

[Rock knocker]

The 1992 Landers earthquake, 7.3 Ricter, was near me and had a maximum offset of about 19'. Given that, exactly where are my property corners now?

Not a bad question, especially now, in the days of satelite surveying.

 

[bcp]

New fault, next to San Andreas fault, discovered under Salton Sea:

Scientists Discover a Second Major Fault Touching the San Andreas | Big Think

"The location of the new fault is especially alarming because USGS seismologists have been worried for some time about what would happen if a major quake started in the Salton Sea area. In 2008, a “ShakeOut” simulation predicted that a magnitude 7.5 quake starting there would be devastating to San Bernadino, with Los Angeles rocked for a full minute — an eternity in earthquake terms — and be felt as far away as Bakersfield, Oxnard and Santa Barbara. It projected roughly 1,600 fires across the state and magnitude 7 aftershocks causing even more severe damage."




Bruce