Not long after, the California emergency response team called him, asking what he could say about the earthquake, because the seismometers had been
152
knocked out by its severity. He told them the direction from which it came, along with its approximate distance (based on the time between different waves, but not the P and S that are normally used, as described earlier). From these he guessed that the earthquake was near Santa Cruz, and he was also able to roughly guess its strength. He boasted to me that for several hours his information was the best available. I must mention, however, that this “expert” is the same friend who bought a house on dredged coastal fill, the worst possible place to be in an earthquake; that is why he was able to view this earthquake so well.
Scope of the problem
To begin to see the scope of the problem of earthquakes and people, let’s consider a few statistics:
• ~150 earthquakes each year are potentially damaging (Mw
6);
• ~20 earthquakes each year cause severe damage (Mw
7);
• in the 1990’s, more than 100,000 people were killed in earthquakes, especially those in Iran, India, Russia, and Japan. This was a worse death toll than usual, not because of more earthquakes but because they happened to affect highly populated areas. By comparison, storm surges killed 300,000 people in 1992 alone, mostly in Bangladesh.
• the largest earthquake of the last 40 years, the Mw 9.2 Sumatra earthquake, created a tsunami that killed 228,000 people;
• globally, the risk of being killed by an earthquake is ~1 in a million per year, similar to the risk of dying in a fire or tornado. Like tornados, there are huge regional variations in earthquake risk.
Effects of earthquakes
Earthquakes affect people mainly by damaging their constructs – buildings, bridges, dams, pipelines, etc. This destruction is economically painful, but