The Nasca Pacific tectonic plate slid 20 to 30 feet under Chile at 10:34 pm on Friday night.  The resulting earthquake was 500 times as powerful as the recent Haitian one, with a Richter Scale value between 8.6 and 8.8.  Earthquakes are neither irregular nor surprising in Chile, a country USGS geophysicist Ross Stein refers to as an “earthquake hatchery.”  Still, 3 million people were exposed to severe shaking, at least 711 died, and the entire Pacific was put on tsunami watch, even right here in the Bay Area.

The initial hazards included not only the distribution of damage caused by shaking, but also the possibility that strong aftershocks might follow.  When there is plate activity along a thrust fault, like the one that exists between the Nasca and South American faults, there is a chance of increased pressure along the ends of the fault activity, resulting in a large aftershock.  In fact, two major aftershocks of 6.9 and 5.8 have hit Chile this weekend, scaring some citizens into sleeping in tents rather than re-entering their houses.

As far as the damage from the shock goes, an official report is yet to be released.  Most times it can depend entirely on how well the structures in the area are built.  In Haiti, where the building structure is notoriously weak, an estimated 70 thousand buildings collapsed, and 10% of people in those areas died.  Presumably, the structures in Chile have been built with increased earthquake awareness, because major earthquakes are a frequent occurrence in their history.  They have a building code that, much like that of the Bay Area, emphasizes earthquake safety.

Haiti, aside from lacking the economic benefits of Chile, has not experienced a major earthquake in over 200 years, so their buildings are not reinforced with iron rebar.  Rebar, said Stein at a press conference this afternoon at USGS, raises the price of constructing a building by 15%, but it can make “the difference between a building that kills people” and one that will survive a major quake.

According to the USGS, tsunamis can travel about as fast as a jetliner.  Their power does not significantly decrease until they hit the shore, so the tsunami triggered by the earthquake hit California at 12:30 pm and Hawaii at 1:00 pm, both on Saturday.  One of the biggest dangers with tsunamis is that they move at about 40 miles an hour, so by the time you can see the swell, it is too late to outrun it.  A half-meter tsunami wave can pull a person out to sea.

In one Chilean coastal town, the tsunami killed over 300 people and wreaked havoc on the harbor and homes.  In Hawaii, however, neither death nor serious damage has been reported. Because they had more than twelve hours to operate, the tsunami warning center in Hawaii managed to completely evacuate the beaches and coastal homes.  In a triumph for the emergency evacuation system, the 6.5-meter tsunami waves crashed onto the shore with little to no effect on the population.

Check back for updates from the USGS on the situation in Chile.