The DGS maintains its own network of seismometers to detect local earthquake activity. Following an earthquake swarm in 1972, the DGS established its first seismometer station in Newark. The network now consists of five seismic stations spread across the state: three stations in the Newark-Wilmington area, one at the DEMA office in southern New Castle County, and one at the Sussex County Emergency Operations Center.
Please answer every question to the best of your ability. Either fill in the blanks where called for, or check the response that best describes the event. If a question does not apply or if you don't know how to respond to a particular question, simply skip it and go on to the next. Feel free to add additional information in the Additional Comments box at the bottom of the form.
Sussex County Emergency Operation Center (SCOM) Seismic Station. The seismometer, located on the property of the Sussex County Emergency Operation Center, is positioned on the Beaverdam Formation. The Beaverdam Formation is a very coarse sand with beds of fine to medium sand. It is interpreted to be a Pliocene fluvial to estuarine deposit.
Delaware Emergency Management Agency (DEMA) Seismic Station. The seismometer, located at the Delaware Emergency Management Agency, is located on the Columbia Formation. The Columbia Formation is a fine to coarse, feldspathic quartz sand with varying amounts of gravel. It is primarily a body of glacial outwash sediment deposited in a cold climate during the middle Pleistocene.
White Clay Creek State Park (NED) Seismic Station. The seismometer, located in White Clay Creek State Park, is positioned on the Wissahickon Formation. The Wissahickon Formation is an extensive sequence of pelitic and psammitic gneisses interlayered with amphibolites. With few exceptions, most of the amphibolite layers are less than 30 feet thick. The rocks have been metamorphosed to upper amphibolite facies and isoclinally folded. The formation is located within the Wilmington North, Kennett Square, West Grove, Newark West, and Newark East U. S. Geological Survey 7.5-minute quadrangles.
Brandywine Creek State Park (BWD) Seismic Station. The seismometer located at Brandywine Creek State Park is positioned on the Wissahickon Formation. The Wissahickon Formation is an extensive sequence of pelitic and psammitic gneisses interlayered with amphibolites. With few exceptions, most of the amphibolite layers are less than 30 feet thick. The rocks have been metamorphosed to upper amphibolite facies and isoclinally folded. The formation is located within the Wilmington North, Kennett Square, West Grove, Newark West, and Newark East quadrangles.
Bellevue State Park (BVD) seismic network station. The seismometer located at Bellevue State Park is placed on the Brandywine Blue Gneiss. The Brandywine Blue Gneiss is the new name given to the granulite-facies felsic gneisses in the Wilmington Complex. Informally called the “blue rocks,” this unit is a medium- to coarse-grained, lineated (pinstriped), two-pyroxene gneiss with variable quartz content and thin, discontinuous mafic layers, pods, and schlieren. The pinstriping and the massive nature of the rock suggest the rock is intrusive; however, deformation and recrystallization have obscured original igneous features.
Natural hazards are those events in the physical environment that present risks to human life or property. The DGS identifies and investigates natural hazards to help understand the earth systems that present the hazards and determine strategies to prepare for or mitigate the risks. We are active in advising emergency management agencies on natural hazards, and are included in the Delaware Emergency Operations Plan as an agency having a vital role in dealing with floods, northeaster/extratropical storms, droughts, earthquakes, sinkholes, and dam failures.
Earthquakes occur in northern Delaware and adjacent areas of Pennsylvania, Maryland, and New Jersey. Over 550 earthquakes have been documented within 150 miles of Delaware since 1677, and 69 earthquakes have been documented or suspected in Delaware since 1871.