How to build your own seismic station by Mauro Mariotti translation by Chris Chapman

Page updated  25 August 2002

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Introduction

Overview

Equipment needed

A remote station

A portable seismic station

The seismic station of Associazione di Protezione Civile di Foligno (PG) - Italy

Seismometers are described in the article, vertical and horizontal sensors. Since the instructions for building the sensors and equipment sold by the Nuova Elettronica magazine are copyright, I can only refer you to that magazine.

I can say from personal experience that the Nuova Elettronica systems are very well made, they function in stand alone mode, are not related to any kind of computer or operating system and they are within the price range of any budget. However, there are some limitations concerning the detailed analysis which is possible with their basic system. With a trace recorded on thermal paper, you are limited to just being able to estimate the distance of the earthquake. You need to have recorded and measured many 'known' events to be able to construct a calibration graph for your equipment and location which is good enough for you to be able to estimate earthquake magnitudes. The limited timing accuracy of the Nuova Elettronica's chart recorder initially only allows the epicentre distance to be estimated. This is particularly true for local earthquakes (we have many in Italy), when you may need to measure the time correct to 1/10 sec or better.

To say a word on the new LX1500 Nuova Elettronica's kit, a step ahead has been accomplished but it presents many limitation factors and even if other kind of software will be used with, it will remains only a training system.

To build a more advanced semi professional system you need to satisfy some additional conditions:

1. The seismic signal should be recorded digitally together with precise timing information
2. The A/D converter range should allow you to record signals which are only just detectable, while not saturating during stronger events
3. Each 'event' should be recorded separately in a single file and be available to be read and analysed using an analisys software
4. This should all be available at low cost, suited to the budget of an amateur seismologist
 

Overview
A typical professional datalogging system may be summarised in the following way:

Equipment needed:
Commercial systems use very accurate sensors, classic amplification and filtering stages and very wide range digitisers (24 bits); they also use microprocessors with dedicated solid state memories (not floppy discs,  but large capacity low power RAM and FLASH memories). This results in a system which is not only very expensive, but one in which the electronics may actually cost more than the sensors! Professional systems may also be designed to meet military specifications, in order to resist the extremes of temperature and other environmental conditions. This gives a huge increase in cost. There are two other factors which you might wish to consider:  During the monitor process you will have only an indicator lights may to signal significant events, there is usually no visual trace to inform the user of what signals are being received. Secondly, if you decide not to continue monitoring earthquakes, it may be difficult to recover much of the cost of an expensive system which was dedicated exclusively to seismic recording.

For a simpler, but more cost effective and informative semi professional system, you might use the following equipment:
 
 

ITEM	made with:
Sensors (from one to three axis)	Purchase sensors /  Nuova Elettronica's sensors / Homemade sensors following the indications in many  web sites
Signal Amplifier	Purchasing or self build with the instructions in these pages
Low pass filter (anti-alias)	Embedded in the amplifier described in these pages
Syncronized clock	Embedded in the a/d board described these pages
GPS time receiver	Purchased in specialized shops or by these pages
DCF77 time signal receiver	Purchased or self made following the instructions contained in these pages
NTP Network Time Protocol using internet	Downloading free softwares capable to syncronize the PC clock (an internet connection is needed)
Data processing unit	A Pentium class or AMD K6 class PC with a datalogging software as the traning software  SEISMOWIN or professional software as SEISLOG.
Storage unit	The personal computer must be equipped with at least 1 Gbytes of mass storage memory.
Remote control	PC-Anywhere, Carbon Copy or with  Windows XP RemoteDesktop
Data analisys and report	BinaWin o Winquake (both are shareware, low cost)

 

Using the proposed solution you will be in the conditions to operate with a wide network already present worldwide and in Italy too. A network born with efforts of fascinated and qualified people, for the achievements of these objectives we have used knowledge from qualified geologists, geophysics, egineers, researchers, tecnicians, programmers and obviously seismologists. A network that already have a standard format for seismic events sharing the "PUBLIC SEISMIC NETWORK format" available even in binary and ASCII for an easy interexchange even for PC world and Macintosh world.
 

A remote station
The station you can see in the picture is one station of the IESN network.
Are visible, some old bottles and stuffs, the personal computer, the 56k modem, an UPS (black box), the digitizer (white box behind the UPS).
The station is remotely controlled by a telephone line, modem and the PC Anywhere software.
The TIME sync is made using the DCF77 radio signal.

Here you can see the 3 sensor for the 3 axis fixed on a metal plate and carefully oriented.
 
 

The cost of the station (sensor excluded) not reach 900 dollars.
The station works continously and records precious data about the local seismicity and regional, and (thanks to the exceptional good geodynamic response of the site) data on worldwide seismic activity.
 

A portable seismic station
To enable you to record seismic events when you are away from home or in a remote area, it is very useful to have a screened metal case to house all the cards, connectors, sensors and other equipment needed. High quality Microphone connectors have been used to link the external hardware, the PC, the DCF77 receiver, the power supply and the sensors.

The picture shows part of the inside of the case. The 3 signal amplifier / filter chains are on the large card and the digitiser is on the small one.

An external view of the mobile station, with the homemade vertical sensor.
 
 

From the left hand side of the picture you can see the box housing the double insulated 220V 15+15V  transformer, the Aluminium case, a Laptop Extensa P133 computer fitted with SEISMOWIN  software, the DCF77 timing receiver in a black plastic box and the cylindrical sensor.

The seismic station of Associazione di Protezione Civile di Foligno (PG) Italy
The Gruppo Volontari di Protezione Civile di Foligno has installed in their operative room a seismographic station based on SEISMOWIN and the boards described in this web site.
Some pictures illustrates the facility.
 
 

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