How many detection centers are necessary to pinpoint the location of the epicenter of an earthquake? Why?

Answer 1

Three...

Triangulation

Answer 2

3.

Draw a dot in the middle of a piece of paper. This is the epicentre of your earthquake. Now imagine you have 1 detection centre (seizmographs is it?) that says this earthquake happened 5 miles away. Scale this down to 5 cm and draw a cross 5cm from your epicentre. Now draw a circle of radius 5 cm around this cross. This circle shows all the possible locations that, according to this one detection centre, the epicentre could be.

Now say another detection centre says an earthquake happened 7 miles away. Again, scale down to 7cm and draw another cross 7cm from your epicentre. Draw your 7cm radius circle and you will see that the 2 circles you now have cross over at 2 points. These 2 points are the 2 places at which the earthquakes epicentre could be. However, you don't know which one it is. You need a third detection centre to tell you this.

Hope this helps, not sure if I've explained it very well.

Answer 3

Calculations are made from several different seismograms, both close to and far from an earthquake source to determine its magnitude. Calculations from various seismic stations and seismographs should give the same magnitude, with only one magnitude for any given earthquake.

Through the joint efforts of the personnel at the USGS in Pasadena and Caltech, we developed a system in 1995 that sent phase picks and event waveforms to the Southern California Seismic Network (SCSN). By the end of 1996, we had implemented the Object Ring Buffer (ORB) real-time software developed by the University of Colorado supported by funding from IRIS. To effect rapid data transfer to the SCSN, and to its successor TriNet, we installed an ORB server on a computer at Caltech, wrote a software module to interface with the TriNet system, and use this mechanism to routinely transfer all the ANZA data within ten seconds of real-time. In this way, the broadband and strong motion data is seamlessly integrated with the TriNet real-time data processing system. In 2000, a full bi-directional real-time data exchange between ANZA and TriNet was established using the ORB system. Real-time data exchanges between UCSD - UC Berkeley (UCB) and UCSD - University of Nevada-Reno (UNR) have been operational since late 1998.

Answer 4

Turtle: you explained it quite well. You did leave out one factor. The earthquake usually is centered below ground. In order to account for the third dimension, you need a 4th detection center to account for depth.