Thread: Frequency vs. Magnitude

Started: 2008-01-22 20:15:52
Last activity: 2008-01-31 17:44:00
Topics: IRIS EPO
Katie Stofer
2008-01-22 20:15:52
From the Maryland Science Center ...

I have a more general question about quakes that I hope one of the
experts can help me with. We have been using a machine to simulate
earthquakes that ostensibly varies magnitude - Pitsco's Epicenter
Earthquake Simulator. They no longer make this and now sell instead the
EQ Tremor Table
http://catalog.pitsco.com/store/detail.aspx?KeyWords=engineering&by=20&ID=4229&c=0&t=0&l=0,
which, instead of magnitude, varies cycles per second (frequency), from
0-30, "in the range of P waves." So, is there a relationship between
frequency and magnitude (the latter being the one that school groups
visiting the science center are more familiar with)? Was our original
machine really varying magnitude (being built, as far as I can tell, on
some sort of belt sander with a variable voltage control), or just
frequency as far as anyone can tell?

Any ideas/insight are appreciated before I rewrite our entire program
due to a broken simulator!

Thanks,
Katie Stofer

--
--
Kathryn Stofer
TerraLink Exhibit Manager
Maryland Science Center
601 Light Street
Baltimore, Maryland 21230
410/545-5976
410/545-5974 fax
BODYWORLDS - Coming to MSC Feb. 2 - Sept. 1, 2008!


  • Michael Hubenthal
    2008-01-28 22:59:58
    Hi Katie,

    I haven't seen a reply to your post yet so I will take a crack at a
    response.

    In short, my guess is that the previous machine took some artistic
    liberties and it sounds like they weren't discussed in the manuals.
    There is a relationship between Period (1/frequency) and Magnitude
    however there are other factors involved. For example the equation
    to determine magnitude using body waves is Mb = log(A/T) + s. Where
    (A) is the amplitude of the P-wave train, the first arriving body
    wave, (T) is the period of the displacement, and (s) is a correction
    term. Larry Braile suggest that for the AS-1 program s=0.01*D + 5.9
    where D is distance to the event.

    The problem with describing the changes in shaking only in terms of
    magnitude only is that it doesn't account for other factors such as
    the distance to the epicenter, regional geology etc. However, the
    folks at Pitsco probably just said, lets assume that all of these
    other factors are held as constants and put a magnitude sticker on
    there (or they may not have even thought about it that much).

    I guess in thinking about your activity, what is the content that you
    want to convey to them?

    Best Wishes
    Michael








    On Jan 22, 2008, at 12:15 PM, Katie Stofer wrote:

    From the Maryland Science Center ...

    I have a more general question about quakes that I hope one of the
    experts can help me with. We have been using a machine to simulate
    earthquakes that ostensibly varies magnitude - Pitsco's Epicenter
    Earthquake Simulator. They no longer make this and now sell instead
    the EQ Tremor Table, which, instead of magnitude, varies cycles per
    second (frequency), from 0-30, "in the range of P waves." So, is
    there a relationship between frequency and magnitude (the latter
    being the one that school groups visiting the science center are
    more familiar with)? Was our original machine really varying
    magnitude (being built, as far as I can tell, on some sort of belt
    sander with a variable voltage control), or just frequency as far
    as anyone can tell?

    Any ideas/insight are appreciated before I rewrite our entire
    program due to a broken simulator!

    Thanks,
    Katie Stofer
    -- -- Kathryn Stofer TerraLink Exhibit Manager Maryland Science
    Center 601 Light Street Baltimore, Maryland 21230 410/545-5976
    410/545-5974 fax BODYWORLDS - Coming to MSC Feb. 2 - Sept. 1, 2008!
    _______________________________________________
    irised mailing list
    irised<at>iris.washington.edu
    http://www.iris.washington.edu/mailman/listinfo/irised

    ---------------------------------
    Michael Hubenthal
    Education Specialist
    IRIS Consortium
    607-777-4612
    www.IRIS.edu
    hubenth<at>iris.edu




    • Jerry R. Cook
      2008-01-28 21:47:23
      Hi All,
      I have a problem with my display that is driving me nuts. Every time the
      display goes to a new line at the end of the hour there is a spike on the
      new line. Check it out at this link;
      http://www.pcds.org/share/earthquake/

      This a real problem if an earthquake happens to span two lines. When I
      extract the event all I get is the spike and the seismic waves are about 1mm
      high. Any suggestions?
      J. Bob




      • Alan Jones
        2008-01-29 00:57:35
        Jerry,

        This could be because you don't have the seismometer zeroed out. A constant offset can cause this.

        Turn off all filtering and make sure the active trace is right on the blue line. With the filtering turned off, do you still get the spiles?

        Are you sure the data shows up as a spike when you extract? It doesn't with me. It's just that each line is filtered separately and there is some start-up problems at the beginning of the line.

        I'm copying John Lahr and the IRIS listserv to see if others have ideas.

        Let us know if this helps.

        Alan

        ############################
        # Alan Jones
        ## AlanJones<at>stny.rr.com
        ### http://home.stny.rr.com/alanjones
        #### 607-786-5866
        ##### 3717 Wildwood Drive
        ###### Endwell, NY 13760
        ############################
        ----- Original Message -----
        From: Jerry Cook
        To: irised<at>iris.washington.edu
        Sent: Monday, January 28, 2008 3:47 PM
        Subject: [irised] Annoying Spikes


        Hi All,
        I have a problem with my display that is driving me nuts. Every time the
        display goes to a new line at the end of the hour there is a spike on the
        new line. Check it out at this link;
        http://www.pcds.org/share/earthquake/

        This a real problem if an earthquake happens to span two lines. When I
        extract the event all I get is the spike and the seismic waves are about 1mm
        high. Any suggestions?
        J. Bob



        _______________________________________________
        irised mailing list
        irised<at>iris.washington.edu
        http://www.iris.washington.edu/mailman/listinfo/irised

      • Jerry Cook
        2008-01-29 03:52:22
        Dear Dr. Jones,
        You rock! When I turned off all filtering the active trace was 21 hours off. Now that I have it centered on the correct hour the spikes are gone. I have no Idea how the trace got so far off. I will add this little gem of knowledge to my list of trouble shooting fixes.
        Cheers,
        J. Bob

        ________________________________

        From: Alan Jones [AlanJones<at>stny.rr.com]
        Sent: Mon 1/28/2008 2:57 PM
        To: Jerry Cook
        Cc: John Lahr; IRISED
        Subject: Re: [irised] Annoying Spikes


        Jerry,

        This could be because you don't have the seismometer zeroed out. A constant offset can cause this.

        Turn off all filtering and make sure the active trace is right on the blue line. With the filtering turned off, do you still get the spiles?

        Are you sure the data shows up as a spike when you extract? It doesn't with me. It's just that each line is filtered separately and there is some start-up problems at the beginning of the line.

        I'm copying John Lahr and the IRIS listserv to see if others have ideas.

        Let us know if this helps.

        Alan

        ############################
        # Alan Jones
        ## AlanJones<at>stny.rr.com
        ### http://home.stny.rr.com/alanjones
        #### 607-786-5866
        ##### 3717 Wildwood Drive
        ###### Endwell, NY 13760
        ############################

        ----- Original Message -----
        From: Jerry Cook <jerry.cook<at>pcds.org>
        To: irised<at>iris.washington.edu
        Sent: Monday, January 28, 2008 3:47 PM
        Subject: [irised] Annoying Spikes

        Hi All,
        I have a problem with my display that is driving me nuts. Every time the
        display goes to a new line at the end of the hour there is a spike on the
        new line. Check it out at this link;
        http://www.pcds.org/share/earthquake/

        This a real problem if an earthquake happens to span two lines. When I
        extract the event all I get is the spike and the seismic waves are about 1mm
        high. Any suggestions?
        J. Bob



        _______________________________________________
        irised mailing list
        irised<at>iris.washington.edu
        http://www.iris.washington.edu/mailman/listinfo/irised



    • John Taber
      2008-01-29 23:46:27
      Katie,

      As Michael says, the key question is what concepts were you
      presenting with your old system? Did the amplitude of the shaking
      appear to vary? If you were primarily talking about building damage
      then varying the frequency may be enough, as building damage depends
      more on the local acceleration of the ground than it does on the
      magnitude of the earthquake.

      If you have someone one on your staff who can build you a new shake
      table you might consider John Lahr's version or any of the other ones
      he lists on his web page: http://jclahr.com/science/earth_science/
      shake/. John may want to comment, but it looks like most of the low
      cost, motor-driven shake tables vary the frequency more so than the
      amplitude.

      John

      On Jan 28, 2008, at 2:59 PM, Michael Hubenthal wrote:

      Hi Katie,

      I haven't seen a reply to your post yet so I will take a crack at a
      response.

      In short, my guess is that the previous machine took some artistic
      liberties and it sounds like they weren't discussed in the
      manuals. There is a relationship between Period (1/frequency) and
      Magnitude however there are other factors involved. For example
      the equation to determine magnitude using body waves is Mb = log(A/
      T) + s. Where (A) is the amplitude of the P-wave train, the first
      arriving body wave, (T) is the period of the displacement, and (s)
      is a correction term. Larry Braile suggest that for the AS-1
      program s=0.01*D + 5.9 where D is distance to the event.

      The problem with describing the changes in shaking only in terms of
      magnitude only is that it doesn't account for other factors such as
      the distance to the epicenter, regional geology etc. However, the
      folks at Pitsco probably just said, lets assume that all of these
      other factors are held as constants and put a magnitude sticker on
      there (or they may not have even thought about it that much).

      I guess in thinking about your activity, what is the content that
      you want to convey to them?

      Best Wishes
      Michael








      On Jan 22, 2008, at 12:15 PM, Katie Stofer wrote:

      From the Maryland Science Center ...

      I have a more general question about quakes that I hope one of the
      experts can help me with. We have been using a machine to simulate
      earthquakes that ostensibly varies magnitude - Pitsco's Epicenter
      Earthquake Simulator. They no longer make this and now sell
      instead the EQ Tremor Table, which, instead of magnitude, varies
      cycles per second (frequency), from 0-30, "in the range of P
      waves." So, is there a relationship between frequency and
      magnitude (the latter being the one that school groups visiting
      the science center are more familiar with)? Was our original
      machine really varying magnitude (being built, as far as I can
      tell, on some sort of belt sander with a variable voltage
      control), or just frequency as far as anyone can tell?

      Any ideas/insight are appreciated before I rewrite our entire
      program due to a broken simulator!

      Thanks,
      Katie Stofer
      -- -- Kathryn Stofer TerraLink Exhibit Manager Maryland Science
      Center 601 Light Street Baltimore, Maryland 21230 410/545-5976
      410/545-5974 fax BODYWORLDS - Coming to MSC Feb. 2 - Sept. 1, 2008!
      _______________________________________________
      irised mailing list
      irised<at>iris.washington.edu
      http://www.iris.washington.edu/mailman/listinfo/irised

      ---------------------------------
      Michael Hubenthal
      Education Specialist
      IRIS Consortium
      607-777-4612
      www.IRIS.edu
      hubenth<at>iris.edu





      • Katie Stofer
        2008-01-30 00:56:33
        Thanks Michael and John -

        Yes, I think the frequency was probably what changed. The amplitude
        varied slightly, too, as the shaking got faster, but I think it wasn't
        the primary variable.

        The program is focused more as a general overview of earthquakes - where
        they occur, when, what magnitude is (just enough to talk about how we
        measure quakes against one another). The building is supposed to be a
        fun, hands-on wrap-up. Many classes treat this either as a good
        summary/reminder of their earlier curriculum or as an intro to an
        upcoming curriculum.
        I guess I was assuming (and implying, though not explicitly stating to
        the students) that the "buildings" were at the epicenter of the
        earthquake, and the quake was in some quake-prone area such as So.
        California. At this point in the program, the "magnitude" was really
        meant to convey stronger shaking to wrap up what I'd reviewed/introduced
        about quakes. I don't go into too much about waves, as I'm generally
        dealing with younger students. I'm only wedded to the current activity
        as it is already created, but the table is failing, and with the new
        version (frequency variable), I was confused about the frequency part
        and its relationship to magnitude.

        For simplicity's sake, were I to get the new table, am I correct in
        saying that as frequency increases, magnitude increases (all else being
        constant), so that as we turn up the frequency, we're approximating an
        increase in magnitude? (as I don't talk about frequency, period, etc. -
        just magnitude).

        Thanks for all your help. Hope this isn't too off-topic!
        -Katie


        John Taber wrote:
        Katie,

        As Michael says, the key question is what concepts were you presenting
        with your old system? Did the amplitude of the shaking appear to
        vary? If you were primarily talking about building damage then
        varying the frequency may be enough, as building damage depends more
        on the local acceleration of the ground than it does on the magnitude
        of the earthquake.

        If you have someone one on your staff who can build you a new shake
        table you might consider John Lahr's version or any of the other ones
        he lists on his web page:
        http://jclahr.com/science/earth_science/shake/. John may want to
        comment, but it looks like most of the low cost, motor-driven shake
        tables vary the frequency more so than the amplitude.

        John

        On Jan 28, 2008, at 2:59 PM, Michael Hubenthal wrote:

        Hi Katie,

        I haven't seen a reply to your post yet so I will take a crack at a
        response.

        In short, my guess is that the previous machine took some artistic
        liberties and it sounds like they weren't discussed in the manuals.
        There is a relationship between Period (1/frequency) and Magnitude
        however there are other factors involved. For example the equation
        to determine magnitude using body waves is Mb = log(A/T) + s. Where
        (A) is the amplitude of the P-wave train, the first arriving body
        wave, (T) is the period of the displacement, and (s) is a correction
        term. Larry Braile suggest that for the AS-1 program s=0.01*D + 5.9
        where D is distance to the event.

        The problem with describing the changes in shaking only in terms of
        magnitude only is that it doesn't account for other factors such as
        the distance to the epicenter, regional geology etc. However, the
        folks at Pitsco probably just said, lets assume that all of these
        other factors are held as constants and put a magnitude sticker on
        there (or they may not have even thought about it that much).

        I guess in thinking about your activity, what is the content that you
        want to convey to them?

        Best Wishes
        Michael








        On Jan 22, 2008, at 12:15 PM, Katie Stofer wrote:

        From the Maryland Science Center ...

        I have a more general question about quakes that I hope one of the
        experts can help me with. We have been using a machine to simulate
        earthquakes that ostensibly varies magnitude - Pitsco's Epicenter
        Earthquake Simulator. They no longer make this and now sell instead
        the EQ Tremor Table, which, instead of magnitude, varies cycles per
        second (frequency), from 0-30, "in the range of P waves." So, is
        there a relationship between frequency and magnitude (the latter
        being the one that school groups visiting the science center are
        more familiar with)? Was our original machine really varying
        magnitude (being built, as far as I can tell, on some sort of belt
        sander with a variable voltage control), or just frequency as far as
        anyone can tell?

        Any ideas/insight are appreciated before I rewrite our entire
        program due to a broken simulator!

        Thanks,
        Katie Stofer
        -- -- Kathryn Stofer TerraLink Exhibit Manager Maryland Science
        Center 601 Light Street Baltimore, Maryland 21230 410/545-5976
        410/545-5974 fax BODYWORLDS - Coming to MSC Feb. 2 - Sept. 1, 2008!
        _______________________________________________
        irised mailing list
        irised<at>iris.washington.edu
        http://www.iris.washington.edu/mailman/listinfo/irised

        ---------------------------------
        Michael Hubenthal
        Education Specialist
        IRIS Consortium
        607-777-4612
        www.IRIS.edu
        hubenth<at>iris.edu








        --
        --
        Kathryn Stofer
        TerraLink Exhibit Manager
        Maryland Science Center
        601 Light Street
        Baltimore, Maryland 21230
        410/545-5976
        410/545-5974 fax
        BODYWORLDS - Coming to MSC Feb. 2 - Sept. 1, 2008!



        • John Taber
          2008-01-31 17:44:00
          Katie,

          For the purposes of a simple demonstration for younger students, and
          if you aren't using it to demonstrate the effects of frequency (ie
          the varying resonance of buildings of different heights) and don't
          talk about increasing the frequency, then I guess you could say the
          magnitude is increasing. If a teacher asks a question, you could
          say that what you really are doing is increasing the acceleration and
          thus the likelihood of damaging the building. We do in our building
          design and destruction exercise where we place an accelerometer on
          the structure.

          John

          On Jan 29, 2008, at 4:56 PM, Katie Stofer wrote:

          Thanks Michael and John -

          Yes, I think the frequency was probably what changed. The amplitude
          varied slightly, too, as the shaking got faster, but I think it
          wasn't the primary variable.

          The program is focused more as a general overview of earthquakes -
          where they occur, when, what magnitude is (just enough to talk
          about how we measure quakes against one another). The building is
          supposed to be a fun, hands-on wrap-up. Many classes treat this
          either as a good summary/reminder of their earlier curriculum or as
          an intro to an upcoming curriculum.
          I guess I was assuming (and implying, though not explicitly stating
          to the students) that the "buildings" were at the epicenter of the
          earthquake, and the quake was in some quake-prone area such as So.
          California. At this point in the program, the "magnitude" was
          really meant to convey stronger shaking to wrap up what I'd
          reviewed/introduced about quakes. I don't go into too much about
          waves, as I'm generally dealing with younger students. I'm only
          wedded to the current activity as it is already created, but the
          table is failing, and with the new version (frequency variable), I
          was confused about the frequency part and its relationship to
          magnitude.

          For simplicity's sake, were I to get the new table, am I correct in
          saying that as frequency increases, magnitude increases (all else
          being constant), so that as we turn up the frequency, we're
          approximating an increase in magnitude? (as I don't talk about
          frequency, period, etc. - just magnitude).

          Thanks for all your help. Hope this isn't too off-topic!
          -Katie


          John Taber wrote:
          Katie,

          As Michael says, the key question is what concepts were you
          presenting with your old system? Did the amplitude of the
          shaking appear to vary? If you were primarily talking about
          building damage then varying the frequency may be enough, as
          building damage depends more on the local acceleration of the
          ground than it does on the magnitude of the earthquake.

          If you have someone one on your staff who can build you a new
          shake table you might consider John Lahr's version or any of the
          other ones he lists on his web page: http://jclahr.com/science/
          earth_science/shake/. John may want to comment, but it looks like
          most of the low cost, motor-driven shake tables vary the frequency
          more so than the amplitude.

          John

          On Jan 28, 2008, at 2:59 PM, Michael Hubenthal wrote:

          Hi Katie,

          I haven't seen a reply to your post yet so I will take a crack at
          a response.

          In short, my guess is that the previous machine took some
          artistic liberties and it sounds like they weren't discussed in
          the manuals. There is a relationship between Period (1/
          frequency) and Magnitude however there are other factors
          involved. For example the equation to determine magnitude using
          body waves is Mb = log(A/T) + s. Where (A) is the amplitude of
          the P-wave train, the first arriving body wave, (T) is the period
          of the displacement, and (s) is a correction term. Larry Braile
          suggest that for the AS-1 program s=0.01*D + 5.9 where D is
          distance to the event.

          The problem with describing the changes in shaking only in terms
          of magnitude only is that it doesn't account for other factors
          such as the distance to the epicenter, regional geology etc.
          However, the folks at Pitsco probably just said, lets assume that
          all of these other factors are held as constants and put a
          magnitude sticker on there (or they may not have even thought
          about it that much).

          I guess in thinking about your activity, what is the content that
          you want to convey to them?

          Best Wishes
          Michael








          On Jan 22, 2008, at 12:15 PM, Katie Stofer wrote:

          From the Maryland Science Center ...

          I have a more general question about quakes that I hope one of
          the experts can help me with. We have been using a machine to
          simulate earthquakes that ostensibly varies magnitude - Pitsco's
          Epicenter Earthquake Simulator. They no longer make this and now
          sell instead the EQ Tremor Table, which, instead of magnitude,
          varies cycles per second (frequency), from 0-30, "in the range
          of P waves." So, is there a relationship between frequency and
          magnitude (the latter being the one that school groups visiting
          the science center are more familiar with)? Was our original
          machine really varying magnitude (being built, as far as I can
          tell, on some sort of belt sander with a variable voltage
          control), or just frequency as far as anyone can tell?

          Any ideas/insight are appreciated before I rewrite our entire
          program due to a broken simulator!

          Thanks,
          Katie Stofer
          -- -- Kathryn Stofer TerraLink Exhibit Manager Maryland Science
          Center 601 Light Street Baltimore, Maryland 21230 410/545-5976
          410/545-5974 fax BODYWORLDS - Coming to MSC Feb. 2 - Sept. 1, 2008!
          _______________________________________________
          irised mailing list
          irised<at>iris.washington.edu
          http://www.iris.washington.edu/mailman/listinfo/irised

          ---------------------------------
          Michael Hubenthal
          Education Specialist
          IRIS Consortium
          607-777-4612
          www.IRIS.edu
          hubenth<at>iris.edu








          --
          --
          Kathryn Stofer
          TerraLink Exhibit Manager
          Maryland Science Center
          601 Light Street
          Baltimore, Maryland 21230
          410/545-5976
          410/545-5974 fax
          BODYWORLDS - Coming to MSC Feb. 2 - Sept. 1, 2008!


          _______________________________________________
          irised mailing list
          irised<at>iris.washington.edu
          http://www.iris.washington.edu/mailman/listinfo/irised


Page built 00:08:19 | v.359e0ab5