The 1998 Pymatuning earthquake occurred in the U.S. state of Pennsylvania

Pennsylvania

The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...

 on September 25, 1998. With a magnitude of 5.2, it was the greatest recorded earthquake

Earthquake

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

 in Pennsylvania's history.

Location

The earthquake's epicenter was at latitude 41°29′24″ N and longitude 80°22′48″ W, about 25 kilometres (15.5 mi) southwest of Meadville

Meadville, Pennsylvania

Meadville is a city in and the county seat of Crawford County, Pennsylvania, United States. The city is generally considered part of the Pittsburgh Tri-State and is within 40 miles of Erie, Pennsylvania. It was the first permanent settlement in northwest Pennsylvania...

; its depth was 5 kilometres (3.1 mi).

Impact

The earthquake caused minor damage in towns near its epicenter and was felt in the states of Ohio

Ohio

Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...

, Pennsylvania, Indiana

Indiana

Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...

, Michigan

Michigan

Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....

, New York

New York

New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

, Illinois

Illinois

Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...

 and New Jersey

New Jersey

New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...

, as well as Southern

Southern Ontario

Southern Ontario is a region of the province of Ontario, Canada that lies south of the French River and Algonquin Park. Depending on the inclusion of the Parry Sound and Muskoka districts, its surface area would cover between 14 to 15% of the province. It is the southernmost region of...

 Ontario

Ontario

Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

 in Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

.

Hydrologic occurrences

After the earthquake many well

Water well

A water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access groundwater in underground aquifers. The well water is drawn by an electric submersible pump, a trash pump, a vertical turbine pump, a handpump or a mechanical pump...

s in the epicentral region began to dry up, while new springs and old wells began to flow. A three-month date range revealed 120 dry household-supply wells. Declines of up to 100 feet (30.5 m) were observed on a ridge where at least 80 of these wells resided. The degree of the damage varied. Some of the wells lost all power or could barely hold their yields, and some of the water in wells turned black or began to smell of sulfur

Sulfur

Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

. An official explanation of these phenomena has not been arrived at, yet the most likely cause is the vertical hydraulic conductivity

Hydraulic conductivity

Hydraulic conductivity, symbolically represented as K, is a property of vascular plants, soil or rock, that describes the ease with which water can move through pore spaces or fractures. It depends on the intrinsic permeability of the material and on the degree of saturation...

of shale rock under this area. In this scenario water could have leaked from the hilltops on the ridge.