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When last week鈥檚 magnitude 7.0 earthquake struck off the coast of Humboldt County rattled Northern California and parts of Oregon triggering a tsunami warning that led residents racing inland, many wondered how that temblor could impact San Diego and Southern California鈥檚 earthquake forecast.

After all, SoCal is often nudged by small quakes along the San Andreas Fault, which runs through Imperial County. But it鈥檚 a bit more complicated than that, says Pat Abbott, 色情视频 geology professor emeritus.

Can you explain the significance of a magnitude 7.0 earthquake? 

I think a good thing to think about with a magnitude 7.0 earthquake is how many of them are there per year around the world? There are about 15, and maybe only one at a magnitude eight or above. So this was a truly significant earthquake by its size alone. 

The Recent earthquake in Northern California was significant, but it didn鈥檛 result in a lot of damage. Is a magnitude 7.0 earthquake strong enough to cause destruction? 

For an earthquake of this size, a tremendous amount of energy is released. Luckily for us, though, it was released offshore and in an area of low population. The major towns affected were Ferndale and Petrolia, small towns. Had you had that same amount of energy released inside a major urban area like San Diego, this would be international news, and we would still be cleaning up the mess. 

We focus a lot on the earthquake because it's something unfamiliar to us. We stand on the earth and we think it's solid ground, and then we find out it moves. It shakes. And then we fantasize or we worry about how bad these earthquakes are. But the simple statement is earthquakes don't kill. Buildings do.

You take a magnitude 7.0 earthquake, stick it out away from population like we just had, and there's no serious consequences. But that same thing inside a city, with that much energy release, and buildings collapse, bridges fall and it's our own buildings that collapse upon us and kill us, not just mother nature all by herself.

When will the next big earthquake hit Southern California? Does the earthquake in Northern California mean it鈥檚 going to happen soon?

We geologists and seismologists know a lot about earthquakes. We could tell you where they're going to occur, about how big they're going to be and how often they've occurred at a place in the past, but we have zero ability to tell you when one of these things are coming. But let's just look at the biggest fault in California, the San Andreas Fault, which is 750 miles long.

The northern segment moved in 1906 in the famous San Francisco earthquake. The central segment moved in 1857 causing the Fort Tejon earthquake. But we come down to the part in Southern California from San Bernardino to Palm Springs and down to the Salton Sea, the segment closest to us, this segment has not moved in more than 300 years.

So when we say that's the segment we're expecting to move next, it's not really a scientific statement as much as it is a historic one. You kind of suspect that one will come next, but Mother Nature doesn't operate on a timetable. It will move when it's ready. Each of those other two segments may move again before the southern one does. We know what's coming. We don't know when.

The earthquakes in Northern California left San Diego totally unchanged. Today is the exact same as it was before that earthquake. It will not have a direct effect on San Diego.

Seismology 300 years ago wasn鈥檛 what it is today. How do we know an earthquake occurred way back then?

There are a lot of studies still going on that are trying to pin down the details, things like studying offset rock layers and radiocarbon dating. All the numbers we've been looking at for quite some time tell us there was a big earthquake along the southern segment around the year 1690.

The main way we know how some of these occur is by digging trenches across a fault, looking for the offset layers, and measuring how far they've been moved apart. The farther apart they鈥檝e moved, the more energy it took. Interestingly enough, one of the world's leading experts on this topic, paleoseismology, is professor , right here at 色情视频.

The earthquake in Northern California resulted in a short-lived tsunami warning for parts of the California and Oregon coasts. Could an earthquake along the southern segment of the San Andreas fault trigger a tsunami?

To have a tsunami, you need, more or less, an instant supercharging of the water to fill it full of energy. Any earthquake that happens on land by a fault moving, it's just sending seismic waves to the ocean. It can disturb the ocean a bit, but it's not going to supercharge it.

With the earthquake we just had, the ocean floor split and moved horizontally. What would be more devastating are the times when one side of the fault drops down or the other punches up. That loads the water with more energy and causes the tsunamis we fear. 

In California, most of the fault movements we get are mostly horizontal slip. But if we go back to 1994 in Northridge, there was a magnitude 6.7 earthquake, and that was what we call a thrust fault when one side is lifted up. And one of the reasons the damages were so heavy there is because it wasn't just a magnitude 6.7 earthquake, but the San Fernando Valley region was uplifted and shaken. So there's more energy put in, more building collapses, more deaths.

How protected is San Diego from tsunamis generated by earthquakes elsewhere?

San Diego's in a relatively good position in regards to tsunamis. And by that, I mean, when you look offshore and you see the Coronado Islands, San Clemente Island, Santa Catalina Island, all those islands are uplifted on active faults, and basically it's like having a whole giant set of barrier walls out there to intercept incoming tsunamis and to take a lot of the energy out of the water before it gets to the shore. It doesn't mean we don't have any dangers - tsunamis from Alaska or Chile reach the San Diego Bay or Mission Bay and knock boats together at marinas and do a few million dollars worth of damage, which is not trivial, but it's certainly not the same thing as we saw in Japan back in 2011, where a water wall goes on shore and kills 19,000 people.

What would you say to Southern California residents who are worried about an imminent earthquake following the earthquake up north?

Well, I think earthquakes do put fear in us because it's the earth operating in a way we don't expect. We think it's solid ground. How can it be shaking and moving? So the thing to do there is not fear, not worry, but recognize that things will be shaken. And that means within your own home, the dangers are from things falling on you or being thrown at you during the shaking.

So, what do you have? Do you have a ceiling fan that's not well secured? Do you have a heavy armoire with dishes that's liable to topple over? In other words, think about what things could fall or be thrown at you. An interesting little tidbit of information: In the Northridge earthquake 30 years ago, 10% of the deaths occurred inside people's homes with their own belongings falling on them.

At home, you're on your own. And that also goes for the outside. Do you have tree limbs that are ready to fall off? Think about what might fall on you or your family or colleagues and hurt them, then take, take action. Move it, cut it down, nail it down so that shaking is not going to cause a disaster in your home or office.