00:00Gracias.
00:30Gracias.
01:00Gracias.
01:57Gracias.
02:05So my name is Stephen Hicks, I am a seismologist at University College London.
02:21So this earthquake in Colombia would have happened due to the ongoing tectonic collisions
02:29around the Pacific, so in this case the eastern Pacific, where we have two tectonic plates
02:34colliding once one sinks beneath the other, and as that plate sinks it sort of bends and
02:40gets deformed, and that bending creates a fracturing in that tectonic plate which can
02:45then sort of run away into a much larger earthquake, and when that sort of fracturing happens it
02:51creates seismic waves that travel up through the Earth to the surface, and that's then
02:55felt a strong shaking by nearby populations and can damage buildings.
03:13The earthquake occurred with a magnitude of 7.4, which is fairly large.
03:21Now, Colombia is sort of no stranger to earthquakes in that it lies close to an active boundary
03:28between two tectonic plates.
03:31The earthquake occurred at a depth of 100 kilometres, or about 60 miles.
03:38So that means that the earthquake, a lot of earthquakes occurred very close to the surface,
03:43like within the upper 10 kilometres, and create a lot of strong shaking.
03:46This earthquake occurred deeper, which means that the shaking is actually reduced, but there's
03:51some sort of peculiar fact of this earthquake occurring quite deep compared to a lot of other
03:58earthquakes that actually might have enhanced the amount of shaking, and that will rely on
04:03some further scientific research to understand why.
04:27So that given the depth of the earthquake at about 100 kilometres depth, it looks like the damage
04:31would be slightly more than what we would do.
04:33Anticipate.
04:34And this is possibly due to the very specific way in how these earthquakes happen in a sinking
04:45tectonic plate.
04:47But of course, we've also seen, because this is a deep earthquake, it's caused fairly strong
04:53shaking over a very wide area.
04:55And so if just a substantial proportion of those buildings are not built to withstand the
05:00shaping, then you're going to see a lot of damage compared to what one might expect.
05:33After a large earthquake, we can expect a huge amount of damage.
05:36We can expect thousands of aftershocks.
05:38Many of these will be unfilled.
05:40They'll just be sort of only recorded by very sensitive seismic monitoring networks.
05:46So they're happy.
05:47I think they've been a magnitude five already.
05:49And of course, aftershocks are important because they can cause an already damaged building
05:54to maybe collapse, even if the shaking from the aftershock is not as strong.
05:59But what we have learned from around the world for these deep earthquakes when they occur,
06:03sort of, you know, about 100 or more kilometers depth, they actually tend to produce fewer
06:09aftershocks than a shallow crustal earthquake.
06:12So again, it's not like a definite correlation, but it wouldn't surprise me if we see fewer aftershocks
06:21than what we expect from this kind of earthquake.
06:38And then in terms of Venezuela, you know, these countries are about a thousand kilometers apart.
06:43There, the earthquake in Venezuela was much shallower.
06:46So it's like almost up a few kilometers or miles of Earth's crust.
06:51So that created a stronger amount of shaking, but over a much more localized area.
06:57It just happened to hit a very populated area.
07:00So a lot of people, the buildings were affected.
07:02Whereas this deeper earthquake in Colombia would have had less strong ground shaking, but over a much wider area.
07:19Our general rule of thumb is that an earthquake shouldn't really trigger another earthquake
07:25if that earthquake is more than sort of the length of the fault that ruptured away.
07:30So for a magnitude 7 earthquake, we typically expect maybe the fault that's ruptured to be a few tens of
07:37kilometers long.
07:38So we shouldn't expect a direct effect further away.
07:42So with Venezuela being about a thousand kilometers from Colombia,
07:47there shouldn't be a direct sort of what we call triggering link between those two earthquakes.
07:54It's like, okay, so this is not many kilometers .
07:57It's Aah!
08:01Oh, my God, we'll find out.
08:01Are you back here?
08:02Okay, there's a call.
08:06Oh!indолн
08:06I'm
08:07¡Gracias!
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