A Few Earthquake Facts

I used to teach earthquake preparedness to bank employees back in the 90's and I've been dredging through long-idled brain cells to pull back some of the info I remember from those days. From what I remember there are still some exciting times ahead for Chile.

Only about 50% of the energy release from an earthquake event comes from the main shock. The balance will come from aftershocks. The expectation is there will be at least one aftershock that will be 1.0 magnitude less than the main shock. Since the main shock was an 8.8 there should be at least one 7.8 in the coming hours or days. That by itself would be a devastating event.

Since earthquakes are measured on an exponential scale, it will take lots of smaller quakes to equal the energy release of the main quake. Dozens of shocks in the 6.0+ range can be expected and hundreds in the 5.0+ range. As I write this there have been 36 major aftershocks (5.0+) in the Chilean event, including one 6.9 (the Haiti earthquake was 7.0). That place will be rocking for some time, and buildings which may have survived the initial event with significant structural damage could end up coming down in later events.

They won't have the problems Haiti had because they've got better construction and their population is spread out better (and they probably won't get a star-studded musical fundraiser), but they will have plenty of problems resulting from this morning's quake.