Columbia Shakes Again and Wonders HOWARD COUNTY

March 17, 1993

It is becoming old hat for some Columbians, but the recent spate of earthquakes has caused others to pause and wonder what it all means.

Not the least among the curious are experts from the University of Columbia's Lamont-Doherty Earth Observatory in New York, who have headed south to set up seismology equipment in hopes that another small tremor occurs. A fourth tremor in seven days, measuring between 1 and 2 on the Richter scale, occurred at 3 a.m. yesterday. It was hardly noticed compared to temblors that measured 2.7 Sunday night, and 2.5 and 2.0 last week, not following the more traditional pattern of aftershocks being of increasingly reduced force.

That is part of the mystery involving Maryland's recent mini-quakes. Not only is the state unaccustomed to such jolts, having experienced only 26 since the first was recorded in Annapolis in 1758, their origins are relatively unknown. Because Maryland doesn't sit on a major fault line, scientists wonder what formations are shifting beneath the earth's surface and how deep they run.

Most of the available information about earthquakes has been culled from areas where they are more frequent and violent, such as in California. But there may be some interesting data to be had from Columbia's minor excitement that would lead to a better understanding of quakes in general.

One thing is certain: Something beneath the earth's surface is out of kilter and releasing enough energy that those of us above ground can feel and hear the consequences. The Columbia quakes are the first to occur in quadruplet in the state, and could suggest a trend or even a more serious quake, researchers said. It could also be the last one for a long time.

All but the most recent quake sent residents in a bee-line for the phone; hundreds called the local authorities to confirm their suspicions. Some residents, on the other hand, are already jaded. "This is our third quake and we've become used to having them," one resident yawned.

So long as Maryland's quakes remain as low-key as the most recent ones, there is no cause for alarm. They do, however, represent a profound mystery. Just as they unnerve us in their sudden intensity, they, along with Saturday's "storm of the century," are reminders of how dependent we are on nature staying in check.

jTC

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