Sumatra Earthquake Seismogram
The image below is a seismogram of the Sumatra earthquake, which occurred at 7:58:53 p.m. Eastern Standard Time, December 25, 2004, or 7:58:53 a.m. local time, December 26, 2004 in Sumatra. The earthquake occurred beneath the Indian Ocean, just off the west coast of northern Sumatra. The seismogram was recorded on the Pennsylvania Geological Survey seismograph at Middletown, Pennsylvania, about 15,000 kilometers (9,000 miles) from the quake's epicenter.
The seismograph at the Middletown office recorded the tremors over 2 hours and 30 minutes, starting at 8:15 p.m. on Christmas Day when compressional (P) waves arrived. Shear (S) waves followed soon after the “P” waves. Large surface waves began arriving about an hour later. Seisomographs around the world, including the one in our office, documented the huge 9.0 earthquake.
For more information about earthquakes, visit the the USGS web page on Earthquakes. See their "EQ Glossary" for more information about earthquake terms and concepts, including the different types of seismic waves.
For more information on December 26, 2004 Sumatra earthquake and the resulting tsunami, visit the USGS web page .