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AS1 Seismic System

The AS1 seismic system is sold by Jeff Batten, who is THE AMATEUR SEISMOLOGIST, 2470 Stearns St. #322, Simi Valley, Ca. 93063.  Contact: amateurseismo@gmail.com

Each year IRIS runs a workshop at which teachers learn the basics of seismology and how to run an AS-1 seismic system.  For more information, see:  http://www.iris.edu/hq/programs/education_and_outreach/seismographs_in_schools

Frequently Asked Questions (FAQ)

Specifications:

Seismometer: Vertical velocity transducer with oil damping.
Natural Period: 1.5 sec (Filter extends bandwidth to 20 sec.)
Amplifier: 100db w/Low Pass Filter -- there is a zero adjustment but no gain adjustment.
Digitizer: 12 Bit Analog to Digital Converter
Bandwidth: .5 sec to 20 sec 
Dimensions: 17" Long, 6" Wide, 10.5" High


Computer Interface: through the serial port to PC.  
Power Supply: Jameco Model EGPS-007, Product No. JE9100
    120 V 60Hz;  Output: +5v/600 mA, +12V/250 mA, -12V/250 mA, Common
Data Format: an ASCII number from 0 through 4095 followed by a CR and a LF at a rate of about 6.2 samples per second.
Price of complete system: $550.00 plus California sales tax if applicable, plus shipping and handling.
Price without seismometer: About $275 plus California sales tax, if applicable, plus shipping and handling.
Price of plastic cover and plastic dish for damping oil: $40.00 from E & A International, 4801 Ellison Street #G NE, Albuquerque, NM 87109 (Tel: 505-345-4101 Fax: 505-345-4101)
Contact: Istvan Matyasi
Alternate Cover -- Plastic Storage Box: $8.99 from Fred Meyer

Schematic Diagram of Operation

Photos:

Here are some photos of the AS1 system.

Software:

A system includes a seismometer and computer interface which work best with the AmaSeis software written by Alan Jones.

Setup and Calibration:

Video by Jenda Johnson showing setup of AS-1 instrument; best viewed in conjunction with reading the Manual written by Tammy K Bravo & Anne M Ortiz

Pictures showing setup and calibration. 

A QuickTime movie showing an instrument being set up.  as-1_seismometer.mov (19 MB)

MS PowerPoint slides on setup and calibration (20 MB).

Setup to demonstrate the sensitivity of the system to very small motions.

An extensive compilation of information and lessons related to the AS1 seismic system has been created by Professor Larry Braile of Purdue University.

Bob Hutt of the USGS Albuquerque Seismic Lab analyzed the response and found that one low-pass pole at 1 s, another at 15 s, and  a high-pass poll at 20 s.  See his American Geophysical Union poster for all of the details.) 

How to test the "AS1 Black Box"

Larry Braile's AS1 page has instructions for the "relative" calibration of an AS1 system: http://www.eas.purdue.edu/~braile/edumod/as1mag/as1mag1.htm

Pictures of lift-test calibrations with varying damping ratio.  If the boom is displaced by 10 mm, then it will return to zero and overshoot by 0.5 mm when the "damping ratio" is 0.7.  This is a good value for seismology.  The damping ratio is defined as the ratio of the current damping to critical damping.  A damping ratio of 1.0 implies critical damping, in which there is no overshoot.  A damping ratio of 0 implies no damping, which in this case would mean an overshoot of 10 mm, so the boom would never stop oscillating.

My lift-test calibrations. 

Tim Long's pages include good photographs and complete instructions for AS1 calibration.  

Each year IRIS holds a workshop for teachers who have received AS1 systems.  Here are some pictures from the November 2005 workshop.

Spring and Mechanical Measurements

Excel spread sheet (in html format)
Excel spread sheet (requires MS Excel)

Damping Oil

The correct damping of the AS1 system depends on the oil used in the damping container.  The best results are obtained by using a combination of STP oil treatment and 10W40 motor oil.  The proportion of these oils that works best depends on which model of AS1 is being used.  Early models used a 4 mm-diameter spring, while later models have an 8 mm-diameter spring.

Square Container Supplied with AS1 Unit

Spring Diameter STP Oil Treatment 10W40 Motor Oil
4 mm 1/3 (1/4 cup) 2/3 (1/2 cup)
8 mm 1/2 (3/8 cup) 1/2  (3/8 cup)

These proportions are for the square container that is supplied with the AS1 unit. The round containers that IRIS supplied should probably not be used, as they add one more variable and tend to leak.

I've just (6/8/2006) come up with a better idea for the oil container!  I'm setting up six AS1 systems that will be shared among 12 teachers in Portland, Oregon.  Transporting an open dish of oil is almost certain to result in a disastrous mess!  I purchased 8 oz plastic jars with screw-top lids from a pharmacy.  Because of the smaller diameter, a mixture of 1/7 STP Oil Treatment and 6/7 10W40 motor oil provided the right damping for these systems with 4-mm springs.

8 oz Plastic Jar from pharmacy with straight sides and 63 mm inside diameter
.

Spring Diameter STP Oil Treatment 10W40 Motor Oil
8 mm* 8 teaspoons 24t or 1/2 cup
4 mm 4 teaspoons 24t or 1/2 cup

*By trial and error I found that for a 4 mm spring the ratio of STP to oil should be 1 to 6.  The thicker, 8 mm, spring will require more STP, but the ratio of 1 to 3 is just a guess.

I found jars locally at a compounding pharmacy for $2 each.  The same jar can be purchased on the web: http://shop.tps-online.com/browse.cfm/4,1084.htm for $62 for 72 jars.  When transporting the AS-1 system, the lid can be placed on the jar to reduce the risk of spilling the oil.  However, the seal is not sufficient to keep the oil from leaking from the jar if turned sidewise for any length of time.

Damping without oil

Chris Chapman has designed a magnetic damping system for the AS-1 that eliminates the need for oil.  A simple setup to demonstrate how magnetic damping works is described here.

Adjusting the damping

When properly adjusted, each peak of the damped oscillation will be 1/20th of the previous peak.  This page show how to make this adjustment.

How to find the coordinates and elevation of your station.

Glitch Problem with AmaSeis/AS1

Filtering in AmaSeis

Keeping the PC's Clock Set

There are free programs available that will go out over the internet to a "time server" run by the National Institutes of Standards (NIST), Time and Frequency Division, to periodically synchronize a computer's clock to accurate UTC time. 

A good, free program for this purpose is AboutTime:  http://www.arachnoid.com/abouttime/.  It is sufficient to have this, or a similar program offered free by NIST, reset the PC clock once every hour.

How to create a real-time helicorder display for the Internet using SnagIt.

It's quite easy to set up a real-time display using the software program SnagIt.  SnagIt can be configured to capture the AmaSeis screen every 10 minutes to a .jpg file.  SnagIt then sends this file via ftp to a web site. 

Instructions for downloading and installing SnagIt

Instructions for setting up the current version of SnagIt

SnagIt uses FTP to send files to the IRIS site.  You can run this simple FTP test to make sure your computer is able to use FTP, as some schools may have this protocol blocked.  If that's the case, your IT department could allow it up for your AmaSeis computer.

How to check if you image is getting to IRIS, or not.

How to create a real-time helicorder display for the Internet using MWSnap

I've posted instructions for an alternative method of sending files using free software.

Setting up the screen saver to use a helicorder image.

Detailed instructions.

Creating a web page on your school's site

Be sure to include "meta" statements within your html <head> area so that the browsers will automatically update to show the latest helicorder record.  As an example, look at the html source code for my station:  College Hill, Corvallis, Oregon.

<meta http-equiv="Refresh" content="600">
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="expires" content="-1">

Real-time displays of AS1 data

Summary page with near-real-time helicorder images of many AS1 stations.

Links on the SpiNet site to many individual, real-time, helicorder records: http://www.scieds.com/spinet/realtime.php

Summary pages of a few earthquakes well-recorded by AS-1 instruments

        Magnitude 6.4 Blanco Fracture Zone, January 9, 2008.

        Two Magnitude 6.5 events on the Queen Charlotte Islands Fault, January 5, 2008.

        Magnitude 5.6 On Queen Charlotte Islands Fault, December 12, 2007.

        Magnitude 7.8 South of Fiji Islands, December 9, 2007.

        Magnitude 7.3 Windward Islands, Caribbean, November 29, 2007.

        Magnitude 3.3 near Maupin, Oregon, November 21, 2007

        Magnitude 5.8 Blanco Fracture Zone, November 19, 2007

        Magnitude 7.7 Chile earthquake, November 14, 2007.

        Magnitude 7.2 N Mariana Islands, October 31, 2007

Magnitude 3.6 near Salem, Oregon, September 24, 2007.

Magnitude 8.2 Southern Sumatra, September 12, 2007.

Magnitude 8.0 Peru earthquake, August 15, 2007.

        Magnitude 8.2 Kuril earthquake, January 13, 2007.

Magnitude 7.6 Pakistan earthquake, October 8, 2005.

Magnitude 9.0 Sumatra earthquake, December 26, 2004
Global wavefield from the Sumatra event.

Magnitude 6.7 Cayman Islands earthquake of December 15, 2004.

KCRG TV in Cedar Rapids, Iowa, on the M 7.9 Tonga quake of May 3, 2006.
Text with link to video

Magnitude 3.3 event recorded on regional station.

Global Seismic Network stations for comparison

USGS Albuquerque Seismic Laboratory helicorder records

Corvallis station, COR,  with toggle between long-period, short-period, and unfiltered broad-band records.

There are several ways you can display the last 24 of ground motion at your school.   The easiest is the USArray station monitor:
http://usarray.seis.sc.edu/.  Just put in your station code or zip code.

If you would like to have the ability to explore a bit more you can use the Rapid Earthquake Viewer:
http://rev.seis.sc.edu/.  Go to Station View and enter your zip code.

Saving one helicorder image per day.

If you are running a program that creates a new helicorder image every 10 minutes, then the technique described here will save one of these images each day.

Find the arrival times at your station for recent events

There is a USGS site that one can use to find the arrival times at your station for a specified earthquake or for all recent earthquakes.  This can help in finding the earthquakes that have been recorded at your seismograph station.  Earthquakes can optionally be selected on the basis of how large the ground amplitude is expected to be at the distance of your station.

Keeping a Station Log

It's a good idea to keep careful notes on your seismic station.  There are three types that are useful.

  1. One notebook can be devoted to technical issues, such as station adjustments, software changes, problems, outages, etc.  Just note the date and time of each entry.
  2. An earthquake log provides a record of the events that have been recorded.  An Excel spreadsheet may be used to create a template for the log that can be printed out.  Here's one that can used to start with:  earthquake_log.xls.  I've also posted a version in HTML, for those without the Excel program:  earthquake_log.html.
  3. I have created an Excel spread sheet to help in finding events that may be weakly recorded.  This may be particularly helpful for learning to recognize earthquake signatures.  Once the spreadsheet (dist_azim.xls) has been downloaded, it can be used to make a table of recent events that includes the distance and azimuth to your station.  This does not involve a lot of typing because the list of recent USGS events located here:  http://neic.usgs.gov/neis/gis/bulletin.asc is copied and pasted into the spreadsheet.  A macro converts from text to columns when "Ctrl d" is pressed.  A graph on the spreadsheet displays magnitude versus distance to your station.  The graph can be printed out and the events that have been recorded marked.  Over a period of time the detection threshold of your station will become clear.

AS1 Links and FAQ's

Larry Braile's Site

Rob Mellors' Site

IRIS has a Seismographs in Schools program that lends AS1 instruments to schools.  Here's one example of the excitement that can be generated!  An application form to receive an AS1 instrument can be downloaded from the IRIS web site.

Early results

On July 6, 2000,  I set up my first AS1 system and was lucky enough to catch an Aleutian earthquake just a few hours later.  Here's what it looked like:

20000707.jpg (222883 bytes)

I'm using software developed by Alan Jones.  With his program, a selected subset of the data can be saved in PEPP, SAC or PSN format for analysis with Larry's excellent WinQuake program.

 

The IRIS Education and Outreach Program maintains a very helpful web site, publishes many educational products which are distributed for free, an runs professional development workshops for teachers at many NSTA meetings. 

Here are some body phases from the magnitude 5.8 southern Sumatera, Indonesia, event of July 8, 2000.

20000708.gif (50497 bytes)

The arrival times shown were determined from the USGS travel-time calculator site, as WinQuake does not display PKP arrivals. 

The surface waves from these two event were below the noise threshold.  That's where a Lehman design with at 15 or 20 s period has an advantage.  There is a second design for the AS1 that can be adjusted to a period of about 2.5 s, which would help somewhat in capturing lower frequency waves.

Central Chile, March 15, 2001

Latest results

Here's a recording of my first Oregon event since moving to Corvallis.  It's an offshore event 333 km away with magnitude Mw 5.6.  The picks shown were automatically placed by WinQuake according to the USGS location and my station location.

Summary

All in all, if you have about $600 and want to begin recording earthquakes quickly, the AS1 system is a possible way to go.  It was easy to set up and start working and is ideally suited for teaching how a seismic system operates.  With the addition of Alan Jones' recording software and Larry Cochrane's WinQuake display and analysis software ($30), one has quite a nice seismic system.

If you have the time to build a long period sensor, then $250 for the AS1 electronics package, plus Alan Jones' software, plus WinQuake ($30) and  you're ready to capture a larger number of teleseisms.  Another option is to purchase Larry's amplifier ($100), AD ($180), and SDR recording package.  When you purchase this package, WinQuake is free, so either way the total cost for electronics and software will be about $300.

Another option would be to just purchase the AS1 sensor for about $250 and then use your own amplifier, filter, and AD.  The DATAQ AD, which costs $150 (or $100 with an educational discount) can be used with AmaSeis.  The full specifications for the various DATAQ AD's are given here: http://www.dataq.com/support/techinfo/dataform.htm .  The model numbers change from time to time.  As of November 2003 the model DI-154RS is the one to purchase.

July 18, 2000 Update

I've tried hooking up my Lehman horizontal instrument to the AS1 electronics.  Yesterday I caught PKiKP from a deep event in the Hindu Kush region of Afghanistan.

000717.gif (35684 bytes)

May 20, 2001 Update

Here's an example of an M6.3 event from Mexico as recorded on the AS1 instrument (top) frame and the nearby USGS long period station (GLD) in the lower frame.

010520.jpg (150797 bytes)

Here's a comparison after applying a low pass filter set to 0.1 Hz to the AS1 seismogram.

010520a.jpg (117068 bytes)

Here's a recording of the M 7.2 earthquake that shook Peru on July 7, 2001.

20010707.jpg (126639 bytes)

Today, October 23, 2001, a series of events occurred near the west coast of Honshu, Japan.  The P-arrivals from the first four of these may be seen clearly on my AS1 record at these times:
 

M6.9    09:08:24
M6.1    09:15:40
M5.9    09:24:24
M6.1    09:46:32

An expanded view of the first three of these events is shown here:

IRIS AS1 Teacher Workshop in Seattle, November 2004
(Much larger version of photo.)

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