A school seismometer

Introduction

Seismic waves form part of the UK National Curriculum (see below) and the seismometer provides an opportunity for experimental work using a data logger or oscilloscope.

Double Science Key Stage 4 Waves — Seismic waves
Pupils should be taught that longitudinal and transverse earthquake waves are transmitted through the Earth, and how their travel times and paths provide evidence for the Earth's layered structure.

Equipment required

• A PC with PicoScope installed
• A Pico PC-based Oscilloscope
• Two seismic probes
• One mallet

Seismic probes

Wooden pegs with sensors available from:

Peter Chamberlain
8 Kingsley Court
New Wanstead
London E11 2SB UK
Tel : 020 8518 8378
Fax : 020 8925 3663
E-mail : PeterChamberlain1@Compuserve.com

Experiment setup

Figure 1: experiment set up

The output of the piezo sensor is connected via a suitable interface such as Pico’s ADC-212 to a laptop computer.

Possible investigations

• Demonstration of the range of seismic waves. The time-scale on the interface is set so that the screen is filled in about 10 seconds. A sharp tap on the ground with a mallet was found to give a more intense seismic pulse than having pupils jumping up and down. The observed range depends on the sensitivity level of the sensor set in the software and the nature and water content of the soil. Certainly ranges of about 3 metres can be detected. Seismic waves generated by trains and road traffic can be detected but sensors need to be close to the wave source. Safety arguments suggest that such experiments are not advisable.
• Estimation of the velocity of seismic waves. (See attached sample results.)
• Detecting seismic waves from different sources such as near a busy road (more sensitive seismic detector required), near a pile driver or with children jumping together.