Frequently Asked Questions

We have compiled a list of frequently asked questions about our seismograph products and services. If you have a question about one of our products or services that is not on this page, please submit a support request.

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What is the richter scale? +

The Richter scale is a measure of the energy released by an earthquake.  It is calculated in a specific way based on a specific type of measuring device.  The scale is logarithmic.  Each unit increase in the scale corresponds to a 10 times increase in the shaking amplitude and a 31.6 times increase in the energy released.  There is no correlation between the Richter scale and particle velocity.

What is the vector sum? +

First of all, the vector sum is rarely used and should be ignored unless there is a need for it to be referenced.  Each time the seismograph takes a sample, there is a value for the radial (longitudinal), vertical and transverse.  The vector sum at that sample is the square root of the sum of the squares of those values.

Example

At time t = 1.0 Second
Radial = 0.30
Vertical = -0.15
Transverse = 0.27

Vector Sum = Sqrt(0.09 + 0.0225 + 0.0729) = 0.43

This is just the vector sum at a time of 1.0 second.  At the next sample time there will be another vector sum value.  The peak vector sum is the largest of all of these values.

What is particle velocity? +

Particle velocity is the velocity of a particle in the ground as a vibration disturbance passes by.  Not to be confused with propagation velocity which is the travel velocity of the vibration.  Whenever a material is vibrated, its particles experience displacement, velocity and acceleration.

A modern blasting seismograph directly measures particle velocity, usually given in units of in/sec or mm/sec.  The measurement is made in three mutually perpendicular directions called the radial (longitudinal), vertical and transverse.  Each vibration will have a greatest amount of particle velocity on each of the three channels.  The peak particle velocity is the largest of these three values.

How do I know if I have bad coupling? +

It is not always evident.  There are two common things to look for which may be indicators.

  1. There is a very low frequency shift in the waveform.
  2. The vertical vibration is much greater than the horizontal vibration or the reverse.

Bear in mind that these indicators could occur for a natural reason.  The best way to avoid coupling issues is to follow the recommendations in the ISEE User Guidelines at www.isee.org.

Does the microphone need to be pointing toward the blast? +

No.  Due to the low frequency content, blast overpressure is omni-directional (the same in all directions).  However, it does not hurt to do this as it gives the proper impression.

Should the microphone be set up in front of the house? +

The ISEE User Guidelines state that If placed too close to a structure, the airblast may reflect from the house surface and record higher amplitudes. Structure response noise may also be recorded. Reflection can be minimized by placing the microphone near a corner of the structure. (USBM RI 8508)

How high should the microphone be off the ground? +

The ISEE Seismograph User Guidelines state that "The microphone may be placed at any height above the ground."

Do I need to use the wind screen? +

Using the windscreen will nearly always be a good idea.  Even a moderate wind can cause a seismograph to trigger continuously if a windscreen is not used and the acoustic trigger is set below 125 dB.

What duration should I use for recording my blasts? +

If you want to record both ground vibration and acoustic overpressure on the same record, the ISEE Seismograph User Guidelines state the following:

  • Set the record time for 2 seconds longer than the blast duration plus 1 second for each 1100 feet (335 meters) from the blast.

In some cases the duration needed may exceed the maximum allowed by the seismograph for the sample rate.  If this happens the only solution is to reduce the sample rate until the required duration can be obtained.  However, before doing this, ensure that the sample rate will be high enough for the expected frequencies.

What are my remote access options? +

There are a number of options for remote access.  Remote access allows you to place a station in location and access the data through a remote connection.  In order to do this it would be advisable to have a security enclosure to hold the seismograph and remote access device.  We can provide a fully configured enclosure designed for this purpose.  Some remote access options are as follows:

  • Cellular IP - utilizes a cellular modem with a static IP address.  Simply use the Seismograph Data Analysis software with your existing internet conection.  Convenient and inexpensive.
  • Dial-up Cellular - utilizes a cellular modem with a dial-up data plan.  Requires a modem on the computer.  Less convenient than IP, but still relatively inexpensive.
  • Dial-up Satellite - utilizes a satellite modem with a dial-up data plan.  Requires a modem on the computer.  Expensive, but works where cellular is not available.
  • Dial-up Landline - utilizes a phone modem on a landline.  Requires a modem at the computer.  A hard wired phone line is needed.
How do I set up a semi-permanent monitoring station? +

A semi-permanent monitoring station has a seismograph in an enclosure with a power source for 24/7 unattended monitoring.  Not only do we provide these as a service, we can also provide all of the necessary hardware so you can do this yourself.  The station normally consists of a specially modified security enclosure, a Mini-Seis seismograph, deep cycle DC battery, solar panel and optionally a remote access option.  Setting up a station is very simple.  Complete instructions are provided.

Where should the seismograph be set up? +

The answer depends on what is being monitored.  The key is to remember that whereever the seismograph is, that is what is being monitored.  If the seismograph is coupled to the ground, then ground vibration is being monitored.  If the seismograph is on a porch, then the response of the porch is being monitored.

According to the ISEE Seismograph User Guidelines, the sensor should be placed on or in the ground on the side of the structure towards the blast. A structure can be a house, pipeline, telephone pole, etc.  Measurements on driveways, walkways, and slabs are to be avoided where possible.  If in soil, the soil should be undisturbed or compacted.  If near a structure, it should be placed within 10 feet (0.3 meters) or less than 10% of the distance from the blast, whichever is less.

What is the proper method to couple the tri-axial sensor package? +

As per the ISEE Seismograph User Guidelines the preferred coupling method is burial, approximately 3 times the height of the package.  The spikes should be pressed firmly into the hole as with surface spiking.  Then the soil repacked around the package.  Use care when removing the package.  Do not pull on the cable to loosen the package.  If using a shovel do not nick or cut the cable.

When burial is not an option, surface spiking may be acceptable.  Firmly press the package with the spikes into a cleared, level area.  Test the coupling by attempting to move the package with your hand.  If the package moves with minimal effort, the coupling is not sufficient.

Please refer to the ISEE Seismograph User Guidelines at http://www.isee.org.

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White Industrial Seismology, Inc.
1206 S. Schifferdecker Avenue
Joplin, Missouri 64801 USA
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