February 25, 1999 Earthquake in Central Maine

Weston Observatory reports that an earthquake occurred at 10:38:43 p.m. Eastern Standard Time on Thursday, February 25, 1999, southeast of Waterville, Maine. It was felt widely through the Augusta-Waterville area of central Maine. It was the largest earthquake in central Maine since December 28, 1988.

The following parameters have been calculated for the earthquake:

Magnitude	3.6 (Mn, local magnitude calculation after Nuttli, 1973)
Location	44.489 North Latitude, 69.539 West Longitude
Depth	approx. 1 kilometer? (shallow)
This places the epicenter about a mile (2 kilometers) northwest of China, in the vicinity of the Winslow-China town line.

Further Information:

At the time of the event, Weston Observatory issued a preliminary determination of its location as about 2 miles east of Waterville, and its magnitude as 3.8. This determination of location and magnitude was widely reported in the news media, even to the unrealistic level of pinpointing the road intersection in Winslow indicated by the preliminary latitude-longitude coordinates. All three local television stations and statewide public radio covered the story on Friday the 26th. Articles ran on Saturday, February 27, in the Kennebec Journal (Augusta), Waterville Sentinel, and Bangor Daily News, among other newspapers.

Within a week, the location had been revised by Weston Observatory to about 2 miles farther southeast with a 3.6 magnitude. The initial determination by MIT placed the epicenter south-southwest of Waterville, about 6 miles west of the preliminary Weston location. On the Preliminary Determinations of Epicenters (PDE) earthquake list of the National Earthquake Information Center, based on calculations by the NEIC at the time of the event, this event is listed at 44.48 N, 69.52 W with magnitude 3.8.

Click to see the seismogram of the February 25, 1999 event recorded at the Waterville, Maine, seismic station. Note that the location and magnitude written on the diagram are the preliminary Weston values, which subsequently have been revised.

The event shows clearly on the Canadian Seismic Network Hourly plot for 3:00 (UT) February 26, 1999.

A press release was issued by the Maine Geological Survey to report general information about the earthquake and to solicit earthquake reports from the felt area. An on-line earthquake questionnaire, developed after the November, 1997 Quebec City earthquake, was used for the first time. Over 500 electronic responses were submitted in addition to many postal reply cards.

Reference:

Nuttli, Otto W., 1973: "The Mississippi Valley Earthquakes of 1811 and 1812; Intensities, Ground Motion, and Magnitudes," Bulletin of the Seismological Society of America, v. 63, No.1, p. 227-248.

Last updated on April 27, 2012