September 24, 2015

Chile keeps having earthquakes

Posted by Austin Elliott

…and keeps surviving them barely scathed.

Maximum tsunami wave height generated by the 16 Sept. 2015 Chile earthquake, from the International Tsunami Information Center

Maximum tsunami wave height generated by the 16 Sept. 2015 Chile earthquake, from the International Tsunami Information Center

Chile has this year been rocked by its 3rd Great earthquake this century–its 14th if you include the last. Though the earthquake’s magnitude and the resulting Pacific-wide tsunami earned it headlines, it was a very mild earthquake in the global scheme of seismic impacts. This has a bit to do with the nature of offshore, subduction zone earthquakes, and a LOT to do with the regulation, education, and cultural integration Chile has accomplished with regard to earthquake risk and resilience.

The death toll is so far only 13, astonishingly small for a magnitude 8.3 earthquake that exposed around 4 million people to strong to severe shaking. In part Chile survived because the main seismic source lay almost entirely offshore, directed out into the ocean where it heaved the water into a significant but not totally catastrophic tsunami. Contrast this with the situation of Kathmandu in its recent earthquake, which ruptured directly beneath the city, lurching the entire place several meters all at once. The other saving grace wasn’t a stroke of luck at all: Chile has invested significantly in preparing for just such an event. In addition, they’ve had plenty of practice with earthquakes of this size. An inventory of past Chilean earthquakes’ low death tolls shows that this quake-prone nation may be one of the safest to be in when a huge quake strikes, which is fearsomely often. The last earthquake to unzip this reach of the subduction zone wasn’t even a century ago, as reported with some brief details on the QuakeHunter blog. The country’s infamy for tremors stretches back centuries and beyond, for example inspiring some ahead-of-his-time musings by Charles Darwin.

The 2015 earthquake overlaid on a map of prior ruptures of the Chilean subduction megathrust, by Robin Lacassin at Institut de Physique du Globe de Paris

A wealth of scientific contextual information about this 2015 “Illapel” earthquake was quickly and impressively assembled by Mika McKinnon at io9. A quick breakdown from the New York Times explains some of the key reasons this magnitude 8.3 earthquake had such a modest human impact. That parallels a longer piece from last April, which followed Chile’s prior great earthquake and explained much about why Chile is such a quake-safe nation, for one that so frequently experiences huge temblors.

The duration and intensity of the shaking is captured in this video from a high-rise condo in Santiago. Of course much of what you see is the tall building’s swaying response rather than the ground’s irregular shaking itself." height="370">

Another loud video from a high-rise in Coquimbo, nearer the epicenter, captures the eerie vision of transformers failing as the earthquake knocks out electricity to the town below.

There are plenty more impressive videos of the earthquake from modern apartment towers, many of which I’ve saved in a YouTube playlist of this earthquake. The swaying condo buildings ride out the earthquake well, as modern towers are meant to do.

Not only are their building codes strong and warning systems efficient, but Chilean citizens have been imbued with an approach of utter calm when temblors strike. Students at a university display a shocking level of calm as the buildings clatter and roar around them during the temblor:

Similarly, another high-rise apartment dweller narrates us calmly through the quake:

This appears to me evidence of a populace with a great deal of experience riding out earthquakes, and also one with few concerns about their impacts. This position may be fair in contemporary Chile, as the frequent, massive earthquakes along the Chilean coast have resulted in very few human, engineered, or economic casualties.

Their sense of calm may stem from their relatively harmless past experiences of earthquakes, but it appears to be propagated by media that remain composed under all circumstances. In the following video clips of live newscasts that were interrupted by the evening quake, you see universally placid reactions from the anchors. The uniquely Chilean “tranquilo” culture during earthquakes is evident in every newscast that was airing at the time of the 16 September quake:

This pair is calm to the point of boredom, as the woman’s impatient faces seem frustrated by the interruption more than anything else:

A supercalm radio host urges his audience to remain calm as well:

The Chilean approach of remaining calm during temblors (“tranquilo,” “mantenga la calma,” and “ya pasó” are heard almost universally in videos of the shaking) is so deeply culturally ingrained that they parody it themselves:

While those of us trained in the Drop, Cover, and Hold On mantra may balk at such blasé responses to vigorous earthquakes, the Chileans may have cause to “mantengar la calma.” Certainly it seems a pervasive approach. There are many more videos showing this and other phenomena during the quake, many of which can be found in my YouTube playlist here, and which may form the basis of some subsequent blog posts.