Thread: October 15, 2006 M6.7 Hawaii earthquake and seismograms

Started: 2006-10-19 18:53:37
Last activity: 2006-10-19 19:27:47
Topics: IRIS EPO
The October 15, 2006 M6.7 Hawaii Earthquake and Seismograms



The October 15, 2005 M6.7 earthquake on the west coast of the big Island
of Hawaii was an interesting event. As with many moderate to large
earthquakes, it occurred suddenly and unexpectedly. Our recent memory
suggests that this was an unusually large earthquake for Hawaii. It is
a observed that Hawaii has many small earthquakes associated with
volcanic activity, the Hawaiian hotspot and the stresses on the oceanic
lithosphere caused by the mass of the large volcanoes that make up the
islands. However, if one looks at the historical earthquake activity of
Hawaii (http://earthquake.usgs.gov/regional/states.php?region=Hawaii),
one finds that earthquakes of about the size of the October 15 event
occur about every 20-30 years. (The general USGS earthquake site is:
http://earthquake.usgs.gov http://earthquake.usgs.gov/.) The
Seismic/Eruption software
(http://www.geol.binghamton.edu/faculty/jones/) can be used to view
Hawaii earthquake and volcanic activity from 1960 to the present.



The attached SAC files are seismograms recorded at the West Lafayette,
Indiana AS-1 station (WLIN) for the Hawaii earthquake. The seismograms
can be viewed with the AmaSeis software
(http://www.geol.binghamton.edu/faculty/jones/). The first seismogram
is the original recording from the WLIN AS-1 seismograph. The second
seismogram is a low-pass filtered version of the original seismogram
with a cut-off frequency of 0.1 Hz (10 s period) to enhance the low
frequency content of the seismogram. The P-, S- and Surface-waves
(Rayleigh waves) are very prominent on the filtered record (this is
really a "classic" seismogram -- the kind that you would see in a
textbook -- because it displays the three types of seismic waves so
clearly). Also, the S minus P time for this seismogram can be used to
determine the epicenter-to-station distance. You can use the AmaSeis
software and its travel-time curve tool to estimate the distance (in
degrees, geocentric angle). One can also estimate the mb and MS
magnitudes from the amplitudes of the unfiltered P- and surface-waves.
The official USGS mb magnitude for this event is 6.3 and the MS
magnitude is 6.6.



If you are operating an AS-1 seismograph, try calculating the magnitudes
and filtering the Hawaii seismogram to distinguish the S-P time to
estimate the epicenter-to-station distance for your record. You can
also use the attached WLIN seismograms (the calculated magnitudes from
the WLIN seismograms are almost exactly equal to the USGS values) or
download data from SpiNet (http://www.scieds.com/spinet/).





New Earthquake and Plate Tectonics Activities



Three new earthquake and plate tectonic activities/resources are
available online.



The first is an activity that uses the 2004 USGS map "Earthquakes and
Faults in the San Francisco Bay Area (1970 - 2003)"
(http://pubs.usgs.gov/sim/2004/2848/). The activity (substantially
revised from an older version that used a 1990 map) can be found at:
http://web.ics.purdue.edu/~braile/edumod/bayarea/bayareaNew.htm
http://web.ics.purdue.edu/%7Ebraile/edumod/bayarea/bayareaNew.htm.
This page also has a link to a PowerPoint file with further information
and illustrations on the map, bay area earthquakes and the M7.8 1906 San
Francisco earthquake.



The second activity is the Plate Puzzle hands-on exercise that has been
significantly revised to make use of the new (2006) "This Dynamic
Planet" map. A new feature of the "This Dynamic Planet" map is an
interactive, online version (http://www.minerals.si.edu/tdpmap/) that
can be used to zoom in on different areas of the world and to view the
excellent ancillary information that is contained on the map. The new
activity can be found at:
http://web.ics.purdue.edu/~braile/edumod/platepuzz/platepuzz.htm
http://web.ics.purdue.edu/%7Ebraile/edumod/platepuzz/platepuzz.htm.



The third new online activity is actually a resource for interpreting
AS-1 seismograms and should be very useful to AS-1 operators (or those
who use the AmaSeis software with seismograms downloaded from SpiNet).
A preliminary version of the resource on interpreting AS-1 seismograms
is located at:
http://web.ics.purdue.edu/~braile/edumod/as1lessons/InterpSeis/InterpSeis.htm
http://web.ics.purdue.edu/%7Ebraile/edumod/as1lessons/InterpSeis/InterpSeis.htm.




I hope that this information and these activities/resources will be
useful to you! Please let me know if you have questions or comments.



-Larry Braile

--

Lawrence W. Braile, Professor and Head

Department of Earth and Atmospheric Sciences

550 Stadium Mall Drive

Purdue University

West Lafayette, IN 47907-2051

(765) 494-5979 (O), (765) 496-1210 (Fax)

E-mail: braile<at>purdue.edu <braile<at>purdue.edu>

Web page: http://web.ics.purdue.edu/~braile
http://web.ics.purdue.edu/%7Ebraile

Departmental web page: http://www.purdue.edu/eas/

SAGE web page: http://www.sage.lanl.gov/






  • Aloha -

    As a quick introduction, I am Ted Brattstrom, at Keaau Middle School on the East side of Hawaii island - and I regret to say my AS-1 was not set up in time :-( :-( (and the electricity went out too!)

    Sunday was an amazing day here - The first quake came when I was having some tea and after a few seconds, I decided that standing on the Lanai outside the house was better than standing inside.

    Water in the 8000 gallon water catchment tank began sloshing back and forth and at one point was enough to slosh one wave out of the tank - my own mini-tsunami!

    7 minutes later, we got the second quake :-)

    Both quakes were interesting in that it was easy to feel two components to the shaking - the first was at a higher frequency - more a rumble/shake that lasted a few seconds (5?) continuing on from this was a delightful longer period swaying (the island doing a hula) somewhere between 1 and 2 seconds per oscillation. It was this motion that went on for 30+ seconds and was responsible for the water sloshing, the house swaying and probably for the 3 things that moved on my shelves.
    (I'm guessing these were the P and S waves...?)

    Later in the day I felt the mag. 4 quake, and on Tuesday morning, we were welcomed to wakefulness by a 3.9 (or so) at 5:26 am. The aftershocks are going on - but all much lower in intesity.

    This link shows the last few days of history, as well as a link to the list of quake information.
    http://earthquake.usgs.gov/eqcenter/recenteqsus/Maps/HI2/19.21.-157.-155.php

    On this map - my school is below the "o" in Hilo where the roads diverge - and my home is in Volcano - to the SW of Hilo - near where the road does a small loop around Kilauea caldera.

    This quake has done two things - make me in a hurry to get the AS-1 going, and making sure I have an updated set of emergency supplies :-)

    Cheers - ted


    ----- Original Message -----
    From: Larry Braile <braile<at>purdue.edu>
    Date: Thursday, October 19, 2006 8:12 am
    Subject: [irised] October 15, 2006 M6.7 Hawaii earthquake and seismograms
    To: irised<at>iris.washington.edu

    The October 15, 2006 M6.7 Hawaii Earthquake and Seismograms

    The October 15, 2005 M6.7 earthquake on the west coast of the big
    Island of Hawaii was an interesting event. As with many moderate to large
    earthquakes, it occurred suddenly and unexpectedly. Our recent
    memory suggests that this was an unusually large earthquake for Hawaii.
    It is
    a observed that Hawaii has many small earthquakes associated with
    volcanic activity, the Hawaiian hotspot and the stresses on the
    oceanic
    lithosphere caused by the mass of the large volcanoes that make up
    the
    islands. However, if one looks at the historical earthquake
    activity of
    Hawaii
    (http://earthquake.usgs.gov/regional/states.php?region=Hawaii),
    one finds that earthquakes of about the size of the October 15
    event
    occur about every 20-30 years. (The general USGS earthquake site
    is:
    http://earthquake.usgs.gov http://earthquake.usgs.gov/.) The
    Seismic/Eruption software
    (http://www.geol.binghamton.edu/faculty/jones/) can be used to view
    Hawaii earthquake and volcanic activity from 1960 to the present.



    The attached SAC files are seismograms recorded at the West
    Lafayette,
    Indiana AS-1 station (WLIN) for the Hawaii earthquake. The
    seismograms
    can be viewed with the AmaSeis software
    (http://www.geol.binghamton.edu/faculty/jones/). The first
    seismogram
    is the original recording from the WLIN AS-1 seismograph. The
    second
    seismogram is a low-pass filtered version of the original
    seismogram
    with a cut-off frequency of 0.1 Hz (10 s period) to enhance the low
    frequency content of the seismogram. The P-, S- and Surface-waves
    (Rayleigh waves) are very prominent on the filtered record (this
    is
    really a "classic" seismogram -- the kind that you would see in a
    textbook -- because it displays the three types of seismic waves so
    clearly). Also, the S minus P time for this seismogram can be used
    to
    determine the epicenter-to-station distance. You can use the
    AmaSeis
    software and its travel-time curve tool to estimate the distance
    (in
    degrees, geocentric angle). One can also estimate the mb and MS
    magnitudes from the amplitudes of the unfiltered P- and surface-
    waves.
    The official USGS mb magnitude for this event is 6.3 and the MS
    magnitude is 6.6.



    If you are operating an AS-1 seismograph, try calculating the
    magnitudes
    and filtering the Hawaii seismogram to distinguish the S-P time to
    estimate the epicenter-to-station distance for your record. You
    can
    also use the attached WLIN seismograms (the calculated magnitudes
    from
    the WLIN seismograms are almost exactly equal to the USGS values)
    or
    download data from SpiNet (http://www.scieds.com/spinet/).





    New Earthquake and Plate Tectonics Activities



    Three new earthquake and plate tectonic activities/resources are
    available online.



    The first is an activity that uses the 2004 USGS map "Earthquakes
    and
    Faults in the San Francisco Bay Area (1970 - 2003)"
    (http://pubs.usgs.gov/sim/2004/2848/). The activity (substantially
    revised from an older version that used a 1990 map) can be found
    at:
    http://web.ics.purdue.edu/~braile/edumod/bayarea/bayareaNew.htm
    http://web.ics.purdue.edu/%7Ebraile/edumod/bayarea/bayareaNew.htm.
    This page also has a link to a PowerPoint file with further
    information
    and illustrations on the map, bay area earthquakes and the M7.8
    1906 San
    Francisco earthquake.



    The second activity is the Plate Puzzle hands-on exercise that has
    been
    significantly revised to make use of the new (2006) "This Dynamic
    Planet" map. A new feature of the "This Dynamic Planet" map is an
    interactive, online version (http://www.minerals.si.edu/tdpmap/)
    that
    can be used to zoom in on different areas of the world and to view
    the
    excellent ancillary information that is contained on the map. The
    new
    activity can be found at:
    http://web.ics.purdue.edu/~braile/edumod/platepuzz/platepuzz.htm
    http://web.ics.purdue.edu/%7Ebraile/edumod/platepuzz/platepuzz.htm.



    The third new online activity is actually a resource for
    interpreting
    AS-1 seismograms and should be very useful to AS-1 operators (or
    those
    who use the AmaSeis software with seismograms downloaded from
    SpiNet).
    A preliminary version of the resource on interpreting AS-1
    seismograms
    is located at:
    http://web.ics.purdue.edu/~braile/edumod/as1lessons/InterpSeis/InterpSeis.htm
    http://web.ics.purdue.edu/%7Ebraile/edumod/as1lessons/InterpSeis/InterpSeis.htm.




    I hope that this information and these activities/resources will be
    useful to you! Please let me know if you have questions or comments.



    -Larry Braile

    --

    Lawrence W. Braile, Professor and Head


    Department of Earth and Atmospheric Sciences

    550 Stadium Mall Drive

    Purdue University

    West Lafayette, IN 47907-2051

    (765) 494-5979 (O), (765) 496-1210 (Fax)

    E-mail: braile<at>purdue.edu <braile<at>purdue.edu>

    Web page: http://web.ics.purdue.edu/~braile
    http://web.ics.purdue.edu/%7Ebraile

    Departmental web page: http://www.purdue.edu/eas/

    SAGE web page: http://www.sage.lanl.gov/







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