The Trembling Earth

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Large quake rolls through Costa Rica


Yesterday morning a hefty M7.6 temblor emanated from the subduction zone beneath Costa Rica, setting buildings swaying, pools sloshing, and people scrambling from Panama to Guatemala.

The death toll stands at two, which is remarkable for a quake of this size that didn’t even hit offshore. This may be due to its moderate depth (40km) and relatively remote epicenter, but there were plenty of people that were rocked hard.

Costa Rica apparently has a rather video-savvy populace because there are already a bunch of videos of the quake hitting, and as usual, I’ve compiled them here for you.

First, we can start with IRIS’s always fascinating animation of seismometer data from the U.S. as the seismic waves from this relatively nearby quake ripple northward across the continent:

 

Seismic waves ripple across the U.S. in this display of actual seismometer data from the Incorporated Research Institutions for Seismology, September 5, 2012

Now let’s get to the video footage. First of all there’s the video that’s been replayed by many news organizations that shows some pretty incomprehensible footage from a flailing camera atop a building. meh.

In a more interesting video that really shows the power of the quake, a garage full of vehicles bounces around in a small town outside of the capitol, ~80 miles from the epicenter. In this video you can really see changes in the direction of motion as differently “polarized” surface waves ripple through. I also find it remarkable to note how much time passes before the really strong shaking begins, perhaps lulling people into a false sense of complacency.

There are other videos of bouncing cars, but none as dramatic as that bus. A couple of security cam videos show heavy shaking of people and goods as the quake hits businesses around the country.

Another video shows lampposts swaying as a (fairly gratuitous?) siren sounds the alarm. Perhaps this is a coastal town and the siren is issuing the initial tsunami warning… otherwise I’m personally a little perplexed by the need for sirens to alert people to an earthquake in progress…

The quake elicits a variety of reactions from clerks and customers at a convenience store, who sprint or saunter out of the store depending upon mood. It looks hot there.

A surprised ex-pat marvels at the power that throws her pool water around, even though she herself felt nothing. This should be familiar to the southern Californians who experienced the 2010 Easter Sunday quake at a substantial distance.

Then there’s the aftermath. In one case a local demonstrates the exact wrong thing to do, showing up at the beach to film a potential tsunami, that he soon learns is not coming. Instead he captures shore-parallel fractures in the sand from gravitational failure during the shaking.

The final video is like a natural advertisement for the quake-preparedness bullet points we advocate in the U.S. The house has suffered minor to moderate structural damage, but it’s intact and habitable. However its contents are a wreck. Broken utility lines, shattered glass everywhere, expensive goods thrown to the floor, doors blocked by fallen furniture, and aftershocks startling you while you survey the damage: it’s exactly the scenario described when we warn people how to prepare for the aftermath of a big quake. Let me leave you with this illustrative lesson:

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First-hand documentaries from the Tohoku quake and tsunami

Several eye-witnesses of the March 11 M9.0 in Japan have posted chilling first-hand footage of their experiences. The following two videos document the entire disaster, from the shaking until deep into the tsunami.

First, here’s the harrowing video taken by a professional storm chaser who happened to be in Otsuchi, Japan doing volunteer work for Save Japan Dolphins when the earthquake roared along the coast. He struggles to keep his balance at the tail end of the earthquake, then they hop in their car and spend eight precious minutes fleeing to high ground with the rest of the alarmed population. These guys are clearly professionals; they have incredible composure. As they navigate their way through town you hear radio correspondence with a second car behind them full of other dolphin activists, the Sea Shepherds. While the tsunami roils its way into the bay from the open ocean, the water level creeps up and floods the seaside industrial buildings. As usual with footage of the tsunami, it keeps on coming, getting higher and higher against all belief.

This next video is unprecedented: a high-def dashboard camera in a bus records the entire event, most of it from in/on the tsunami! It was recently recovered, and we get to witness its journey. It would be marvelous if someone who knows Japanese could do a little translation of this report. Watch this; the following text is a spoiler.

It’s incredible to watch as the bus helplessly bobs with mounds of urban flotsam, but the literally immersive perspective reveals fascinating gradients in the velocity and height of the tsunami’s flow as it rages through city streets. The bus seems for a while fortunately stuck in an eddy behind a huge concrete building… until it gets entrained in a rapid flow and slammed up against something, at which point debris pierces the windshield, water rushes in, and the camera dies.

There’s at least one more street-level recording of the tsunami pouring into town. Once again what begins high and dry ends up so far below water it defies imagination.

Videos of the 7.0 and 6.3 in Christchurch

Other than that first video I linked to in the last post and the many recordings of aftershocks, very little footage of the 6.3 occurring exists. I have found only this, in addition to the frequently replayed clips from a liquor store and of the cliff collapsing.

There’s also a decent video of the early morning September quake impressively heaving cars around in a dark driveway. If anyone knows of or finds other videos of the 6.3, feel free to share them here.

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