"There was a 10-year period where thing were pretty quiet," he said, "but we're seeing more earthquake activity now."

Eleven of these were used to monitor earthquake activity, while the other eight also record information on the island's geothermal areas.

This was closely followed by an upsurge of earthquake activity in April 2004.

The Virginia seismic zone has not had a history of regular earthquake activity.

Visitors can search the on-line database of recent earthquake activity.

The last period of heightened earthquake activity probably took place during the Triassic, 200 million years ago.

Faults are visible indicating significant earthquake activity between 80,000 and 13,000 years ago.

They try to predict the future largely by revealing past patterns of earthquake activity.

So there was a lot of earthquake activity to produce these features.

We found that none of these pages report any earthquake activity for our area on 4/11.