A Shaky Situation With Dangerous Potential

June 17, 2005 — -- Seismologists study earthquakes, and they will be the first to tell you their science is very young and sometimes very frustrating. Mother Earth is still hiding many details of how giant blocks of her crust move and grind and bump into each other, the type of planetary movement called plate tectonics that pretty much provides the energy for all earthquakes.

This week California got rattled several times, and whenever a series of large quakes gets our collective attention (especially whenever the word tsunami is attached), questions arise of how they might be related to each other. That's a very legitimate question, but it's fraught with scientific uncertainty.

Thursday's quake near San Bernardino, Calif., for instance, was very close to (if not right on) the famed San Andreas Fault, which runs through San Francisco (Daly City to be exact) and then southeastward all the way to and beyond the Los Angeles area. Tuesday's temblor, however, was offshore to the west of Eureka, Calif., many hundreds of miles northwest of San Bernardino, and at first blush completely unconnected with the San Andreas.

But recent geologic history has too often taught us things we hardly suspected, and because all of us (including seismologists and geophysicists) are always looking for patterns, it's tempting to think that two quakes in California in two days may be a harbinger of more to come.

One may beget another, so to speak.

When we're thinking about a second quake in the same area, that's well understood and entirely possible. Most West Coasters, especially, know that even a large quake could be what's known as a foreshock of what could be a following larger quake.

And, there's the question of pressure along any of the myriad faults which underlie the Los Angeles area. Did it increase or decrease? One highly experienced seismologist was asked that exact question Thursday: Did the quake in San Bernardino relieve or increase the stored, dynamic tension along the San Andreas?