Locating earthquakes, datalogging and software

Using triangulation to locate an earthquake.

By looking at the seismograms from different recording stations we can find out the epicentre of an earthquake.

The signals arrive first at the closest station and last at the one furthest away.

The time difference between the P- and S-waves tells us the distance the earthquake is from the seismograph.

By measuring the time difference at three stations we can work out where the epicentre is.

We need measurements from at least three stations to find the epicentre.

The intersection of the circles, whose radius is equivalent to the distance from the earthquake, gives the epicentre.

Educational software

Seismologists, both amateur and professional, record and exchange data using standardised data formats and protocols. There are many software tools that are available to read and work on seismic data that has been recorded by schools or professional seismic networks.

SeisGram2Kand jAmaSeis are both free-to-download software that have been designed with educational users in mind.

SeisGram2K

jAmaSeis filtered spectrogram

SeisGram2K is a general purpose seismogram analysis toolkit that has been modified to be useful for schools.

The software is free to use and is written in Java so will run on any computer that has Java installed. You can download the latest SeisGram2K software from ALomax Scientific.

'Quick Start: You can launch SeisGram2K directly from the SeisGram2K70.jar class file archive'.

ALomax also provide a simple pdf user guide for schools. Download SeisGram2K-School Users Guide 2.5MB pdf from ALomax.

This software can read seismograms in any of the common data formats used by seimologists and is suitable for both data that you have recorded yourself and data that you have downloaded from the web.

jAmaSeis

Designed specifically for use by schools, this free software allows users to record, view and analyse data from a wide variety of simple seismic sensors.

Networked computers can also share the data that they record with other users around the world in real time and users without their own sensor can use the software to view data from other stations in the UK and worldwide.

The software is written and supported by the IRIS educational consortium in the USA. Go to the IRIS website to download jAmaSeis.

jAmaSeis is written in Java and runs on any computer — even a Raspberry Pi.

jAmaSeis users can:

  • obtain and display seismic data in real-time from either a local instrument or from remote stations
  • filter data
  • fit a seismogram to travel-time curves
  • triangulate event epicentres on a globe
  • estimate event magnitudes
  • generate images showing seismograms and corresponding calculations

Note:
To make full use of this software your school firewall needs to allow access to non-http data streams from a remote data centre at http://jamaseis.iris.edu:8080

Seismograms on the internet

After a newsworthy seismic event, it is possible to download seismograms from professional seismic stations around the world in order to do your own analysis.

The easiest place to do this is through the IRIS WILBER3 data portal. This portal allows you to interactively select the event you are interested in and then choose which seismic stations you want to look at.

WARNING:
This portal allows access to terabytes of data from thousands of seismic stations around the world. To make life easier, it is best to limit yourself to looking at data from just one or two stations.

Data from UK stations are archived under the network code GB.

For example, the closest seismic site to BGS Keyworth offices is site station CWF (Charnwood Forest) on network GB.

Each station records data on at least three components, from either vertical or horizontal instruments. For beginners it is best to stick to data from channel BHZ (vertical data).

Related topics

p-wave Seismic waves

P-, S- and surface waves, how seismic waves travel, looking at seismograms.

Macroseismic mapEarthquake intensity

This is a measure of how much the ground shakes at a particular point.

Magnitude spheres.Earthquake magnitude

Magnitude is a number that indicates how much energy an earthquake has released.

Classroom activities

How do seismologists locate an earthquake?How do seismologists locate an earthquake?

This activity uses two microphones to represent two seismic monitoring stations.

What does a seismogram show?What does a seismogram show?

Identifying the parts of a seismogram; P-waves, S-waves and surface waves.

The Kent, April 2007 earthquakeIdentifying features of a seismogram

Students can identify some features on real seismograms or differences in arrival times of P- and S-waves at different stations.

Earthquake triangulation Locating earthquakes in volcanoes

Using data from a recent volcanic eruption, students can do an earthquake location exercise using real data.