San Diego Geologist Discusses Recent 5.7 Earthquake
Tuesday, June 15, 2010
A 5-point-7 earthquake hit the San Diego-Mexico border region last night.
SAN DIEGO DWANE BROWN: You may have felt it last night. A 5.7 earthquake hit the San Diego-Mexico border region. Joining us to talk about the quake last night is Dr. Pat Abbott, Professor Emeritus of Geology at San Diego State. Dr. Abbott, why do you think this was an aftershock to the deadly 7.2 quake on Easter Sunday.
DR. PAT ABBOTT (Geology Professor): Well, basically because it’s right on the exact same area where the movement ended on April 4th. And that’s really what an aftershock is – it’s continuing motion along the same fault or a very closely adjoining fault. And we’re right there – right exactly where the Easter one ended.
BROWN: Well, it felt like the strongest quake since that time, would that be accurate?
DR. ABBOTT: Well, we look at the 5.7 and of course for us, normally that’s a big earthquake. Although it’s small of course compared to the 7.2. But one of the things we’re going to find out today is the fault movement may have gone in a different direction. It may have actually moved to the southwest. And if so, that would explain why there was some greater jolt of energy in San Diego, because more of the energy may have been directed to San Diego rather than alongside the city.
BROWN: I felt the one on Easter Sunday. It felt like it moved backwards and forwards. Last night, it felt it moved left to right and backward and forward.
DR. ABBOTT: I think that may be because of the different movement directions on the fault. We always say here’s an epicenter. Here’s a magnitude. And those numbers and the site all sound very uniform, but in fact there’s different levels of energy that go off in different directions and different kinds of seismic waves carry more energy in different directions. In other words, not everybody experiences the earthquake the same. And that’s why we’re thinking that maybe this fault had actually moved to the southwest, which would have dumped more energy and a different kind of energy into San Diego and that maybe why it was as unique as experience as it was for a magnitude 5.7.
BROWN: Thank you sir for your time.
DR. ABBOTT: Ok
BROWN: At least 45 aftershocks were recorded after the quake last night, the largest measuring 4.5.
To view PDF documents, Download Acrobat Reader.