Thread: Viewing today's M6.8 earthquake with AmaSeis

Started: 2006-09-01 13:24:44
Last activity: 2006-09-01 13:24:44
Topics: IRIS EPO
John or Jan Lahr
2006-09-01 13:24:44
Today's earthquake is a good one on which to try out the helicorder
filters of AmaSeis.

In the latest version of AmaSeis a bug in the filtering algorithm has
been corrected so that it's now possible to view the main helicorder
screen with a strong filter to enhance the lower frequency surface waves.

First off, if you're not running Version 1.1 Level 2006.06.24, then
install this version. Just go to Alan Jones' web site for

Then in the Settings/Helicorder area, turn on low-pass filtering with
a corner at 12 seconds and high-pass filtering with a corner at 25
seconds. This will enhance waves with periods between 12 and 25
seconds. Increase the helicorder gain by a factor of ten at the same time.

Once this change has been made, the surface waves from today's event
should show up quite well.

Remember that changes to the helicorder settings only change the way
the data is displayed in the helicorder window. They do not change
the data that is stored on disk, so the filter settings and gain can
always be changed back to view closer events with higher-frequency
content. The helicorder-filter settings are not applied within the
event window, so filters will have to be reapplied there to enhance
the lower frequencies.


X-SA-MPREASON: authorized domain (


Geographic coordinates: 6.766S, 155.471E
Magnitude: 6.8 Mw
Depth: 53 km
Universal Time (UTC): 1 Sep 2006 10:18:53
Time near the Epicenter: 1 Sep 2006 20:18:53
Local time in your area: 1 Sep 2006 03:18:53

Location with respect to nearby cities:
62 km (38 miles) S (188 degrees) of Arawa, Bougainville, PNG
129 km (80 miles) W (265 degrees) of Chirovanga, Solomon Islands
212 km (132 miles) NW (314 degrees) of Gizo, Solomon Islands
577 km (359 miles) WNW (301 degrees) of HONIARA, Solomon Islands
935 km (581 miles) E (91 degrees) of Lae, New Guinea, PNG

event ID : US scaw
version : 6
number of phases : 112
rms misfit : 0.86 seconds
horizontal location error : 8.0 km
vertical location error : 19.0 km
maximum azimuthal gap : 43 degrees
distance to nearest station : 574.0 km

Flinn-Engdahl Region Number = 193

This event has been reviewed by a seismologist at NEIC
For subsequent updates, maps, and technical information, see:

National Earthquake Information Center
U.S. Geological Survey

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18:05:45 v.22510d55