Locating Earthquake Epicenters Presented By Travis Kane

Vocabulary Epicenter: the point on Earth’s surface directly above an earthquake’s focus. Primary Waves: waves of energy released during an earthquake, that work by compressing particles in rocks. Secondary Waves: waves of energy released during an earthquake, similar to primary waves, except they move more slowly in a transverse wave. Seismic: Of or relating to movement of the earth’s tectonic plates.

Vocabulary Seismograph: An instrument that records ground oscillations, e.g. those caused by earthquakes, volcanic activity and explosions. Magnitude: The magnitude is the size of the earthquake, measured on the Richter scale SCSN: Southern California Seismic Network

Locating the Epicenter When an earthquake occurs, readings of magnitude of the earthquake are taken from different seismographs in different locations. With these, scientists can determine the time between the P-waves (primary waves) and the S-waves (secondary waves) By determining the length of time between the two waves, scientists can determine how far the epicenter was from each station. If the waves are farther apart, the epicenter is farther too. Using that information, they are able to triangulate the epicenter of the quake.

Seismographs Scientists use several different types of equipment to monitor the earth’s tectonic activity.

Seismographs The most commonly used instrument is the seismograph. This is the basic design of a seismograph, a large weight, holds the writing implement in place while the earth moves under it, creating a pattern with many ridges.

Seismograph stations monitor the time in between the arrival of the P waves, and the S waves.

Networks Scientists that are monitoring large areas use different systems, automated systems that use electronics to discover the magnitude of the earthquake, and the epicenter.

Networks Large networks of these seismograph reading stations are spread out, and are very numerous in order to collect a multitude of data.

Networks The picture on the right is the SCSN (Southern California Seismic Network). Each triangle and circle represents another monitoring station.

Locating the Epicenter First, there are three readings from three different stations, A, B, and C. A C B

Locating the Epicenter Station A discovers that it is approximately 350 kilometers away from the earthquake. Because of this, the scientists can draw a perimeter as to where the quake might be. A C B

Locating the Epicenter Station A discovers that it is approximately 350 kilometers away from the earthquake. Because of this, the scientists can draw a perimeter as to where the quake might be. A 350 KM C B

Locating the Epicenter Station B finds that it is four hundred miles from the earthquake. A C B 400 KM

Locating the Epicenter There are now two possible location for the earthquake to have been in. A C B

Locating the Epicenter Finally, Station B reports that it was 420 kilometers from the epicenter. A C 420 KM B

Locating the Epicenter The Scientists now know approximately where the epicenter of the earthquake was. A C B

Quiz How many different seismograph readings are required to determine the epicenter of and earthquake? Define what an epicenter is How does the time in between P and S waves relate to the distance of the epicenter? What does (SCSN) stand for?

Define what an epicenter is Which is most likely to be the epicenter of this earthquake, given the information recorded by the earthquake monitoring stations? How many different seismograph readings are required to determine the epicenter of and earthquake? Define what an epicenter is How does the time in between P and S waves relate to the distance of the epicenter? What does (SCSN) stand for? 3. 250 M 2. C 350 M A 1. B 200 M 4.