Where did our waves come from?
L Braile, 9/12/09, AS-1 Seismograph Workshop, San Antonio
http://web.ics.purdue.edu/~braile/new/Where.ppt
Exploring Planet Earth
Where did our waves come from?
1. Where is source?
a. Seismicity map
b. Epicenter to station distance
c. Hypocenter information (latitude, longitude, depth,
origin time), magnitude, damage/impact
d. Accessing earthquake data:
http://web.ics.purdue.edu/~braile/edumod/eqdata/eqdata.htm
Where did our waves come from?
2. How did the waves get to our seismograph?
a. Earth structure
b. Wave propagation through the Earth
c. Seismic wave phases
d. Seismic Waves software
1. Where is source?
IRIS Seismic Monitor
http://www.iris.edu/seismon/
IRIS Earthquake Browser
http://www.iris.edu/servlet/eventserver/map.do
IRIS Seismographs in Schools Interactive Earthquake Map
http://www.iris.edu/hq/ssn/events
Displaying earthquake epicenters using Google Earth
http://neic.usgs.gov/neis/epic/kml/
http://neic.usgs.gov/neis/epic/epic_global.html (USGS earthquake search)
USGS Earthquake Site
http://earthquake.usgs.gov/
USGS M5+ Recent Earthquake List
http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/quakes_big.php
USGS Earthquake Search
http://neic.usgs.gov/neis/epic/epic.html
IRIS Event Search
http://www.iris.edu/quakes/eventsrch.htm
2. How did the waves get to our seismograph?
Earth
Structure
and
Properties
Seismic Wave Propagation (slinky, human wave demo, seismic
wave animations, seismograms, seismic waves software)
http://web.ics.purdue.edu/~braile/new/SeismicWaves.ppt
Refraction of light by
water
Refraction
Refraction
PKP
Exploring Planet Earth
Epicenter Plotting – year long activity – map practice that
engages students in global earthquake activity
Seismograms recorded by your seismograph from
locations around the world
Using the Seismic Eruption Software…
Seismic-Eruption
software (Free!, Windows)
Introduction and Navigation
California Earthquakes
So. California Earthquakes
Frequency-Magnitude
Analysis - California
Northridge Earthquake (map,
cross section)
Aftershocks (Denali, Landers)
The Seismic Eruption software:
http://bingweb.binghamton.edu/~ajones/
Exploring Planet Earth
The Seismic Waves program
From Alan Jones, SUNY, Binghamton
http://bingweb.binghamton.edu/~ajones/
The Seismic Waves program: Uses speeded-up
time views of wavefronts to illustrate wave
propagation through the Earth. Note reflection,
refraction and wave conversion at layer
boundaries. Seismograms show arrivals of
various phases (wave types and paths). Wave
energy/propagation represented by wavefronts. Raypaths show
direction of travel of a specific point on the wavefront.
Earthquake
Cross Section
Through Earth
Stations for
Seismograms
*
Wavefront
Ray Path
Seismograph
Ray Path is perpendicular
to wavefront
Practice/Demonstation:
The Seismic Waves
Program
Earthquake
Cross Section
Through Earth
Stations for
Seismograms
*
Wavefront
Ray Path
Seismograph
Ray Path is perpendicular
to wavefront
You can add views to the Seismic Waves
Program for “your” seismogram and
other AS-1 (or other) stations. Example:
M6.0 February 21, 2008 Wells, Nevada
earthquake. For this event, we have five
AS-1 seismograms recorded by IRIS
Seismograph in Schools stations!
Earthquake
Cross Section
Through Earth
Stations for
Seismograms
*
Wavefront
Ray Path
Seismograph
Ray Path is perpendicular
to wavefront
Procedure:
1. In AmaSeis, navigate to the selected event. Navigation can be
performed with the Go To Date-Time… tool in the Settings menu, or
with the Forward/Backward control (see below) opened by clicking on
the green arrows on the toolbar, or by scrolling. (You can also
download other seismograms in sac format for Seismic Waves from the
IRIS DMC using Bud/Wilber - http://www.iris.edu/data/request.htm. )
Green
Arrows
Forward/Backward toolbar
2. Extract the seismogram and save as a sac file (Sac is standard file
format that is used by AmaSeis). Use the standard SIS naming
convention (yymodahrmnNAME.sac).
3. Open the Event… dialog box under the Settings menu. A. Enter the
event name (use the same event name for all seismograms that
will be included in the Seismic Waves view). B. Enter the
earthquake magnitude and, C. the earthquake origin time and location.
A.
C.
B.
4. Click OK in the Event Dialog box and the seismogram will display
additional information (earthquake location and magnitude and
epicenter to station distance in degrees).
5. Open the Event Dialog box again and click on Create files for Seismic
Waves to add the seismogram to a folder in the SW (Seismic Waves)
folder. You can add several seismograms from different stations for the
same earthquake. For our Wells, Nevada example, the folder is labeled
2008022114 (see below for path), the date and hour of the event. Five
seismograms have been added to this folder.
6. When you finish adding data to the seismogram folder for your event
(for example, the 2008022114 folder for the Wells, Nevada earthquake
data), an event file will have been created in the SW folder
(2008022114.evt in our example, below). Double click on the folder to
open in Notepad. The evt file will have only one STATION FILE listed.
Add the additional STATION FILES lines to the list (as below) and save.
7. You can also change the TIME ACCELERATION and TIME WINDOW
settings (or others) in the evt file if desired (see settings below chosen
for the Wells, Nevada earthquake seismograms). Save the evt file.
8. You are now ready to open Seismic Waves and run the program for
your event with the added seismograms. The results for the Wells,
Nevada earthquake seismograms are shown on the next two slides.
The seismograms for our example are listed below. Click on the links
to download the sac files and place in your AmaSeis folder (create a
folder called SacFiles for your individual seismograms). You can
open the seismograms in AmaSeis and then export to Seismic
Waves using the Create files for Seismic Waves selection in the
Event Dialog box and you will be ready to view in Seismic Waves.
http://web.ics.purdue.edu/~braile/new/0802211417AZAZ.sac
http://web.ics.purdue.edu/~braile/new/0802211418PCAZ.sac
http://web.ics.purdue.edu/~braile/new/0802211418UPOR.sac
http://web.ics.purdue.edu/~braile/new/0802211421NLNC.sac
http://web.ics.purdue.edu/~braile/new/0802211421WLIN.sac
The Seismic Waves program showing events that can be
viewed, including the Wells, Nevada earthquake
The Seismic Waves program showing the Wells, Nevada
earthquake seismograms from the AS-1 stations. The view
includes Earth surface, Earth cross section and seismograms.
M6.0, February 21, 2008 Wells, Nevada earthquake shown by large red star. SP circles (from S-P times from seismograms analyzed using AmaSeis for
stations PCAZ, UPOR, WLIN and NLNC – red triangles).
-130
50
-70
50
40
40
30
30
20
-120
-110
-100
-90
-80
M4+ earthquakes,
1980-2009 (Sept.
15); about 35,000
events.
-130
-120
20
-110
-100
-90
-80
-70
Input information (left) for
Wells, Nevada earthquake
and location and S-P inferred
distances (radius in km) for
seismograph stations PCAZ,
NLNC, UPOR, and WLIN.
Legend (depth of focus scale
and magnitude and data
source table) for the seismicity
map on previous slide.
Map produced with IRIS event search tool:
http://www.iris.edu/quakes/eventsrch.htm