It is frustrating for those of us that are awake while the NEIC
is sleeping!  Often a quake will occur, but we have to wait for
hours (I've waited for a much as 17 hours) to find out where
the quake was.  I do not have a seismograph, but do check the
seismograms at http://aslwww.cr.usgs.gov/Seismic_Data/heli2.htm
every few hours.

I have been using AutoDRM to receive the data, convert it to
PSN format, and then look at the waveform in WinQuake.  With
the new feature of being able to ask WinQuake for a location,
it is a big help in determining where the quake was.  But,
I was wondering how accurate it would be to compare P-wave
times to known earthquakes to determine the general location.

Recently I finished inputting about 1 1/2 years worth of P-wave
arrival times in an Excel spreadsheet.  I took the information
from the "Big Quake" e-mails sent out by the NEIC.  I find the
results "interesting".  Here's an example of how it works.

There was a quake that occurred at around 03:40 UTC on 12/19/99.
That was about 6 hours ago as I write this.  The last time I
checked the NEIC has not reported this quake.  The Russian's
reported it to RedPuma as:

19Dec1999 03:38:31.6  3.9S 131.6E 33 MS=5.6 IRIAN JAYA REGION

I used AutoDRM to get the data from most of the stations listed
at the above web site.  After converting the data to psn format
and looking at the 'grams in WinQuake I found that I could get
3 good P-wave times.  They were:

CTAO 03:43:20.1     YAK 03:49:14.7     TIXI 03:50:11.7

Those times were arrived at by my moving the P marker and looking
at the time that WinQuake showed.  Then I used Excel to help me
determine the difference in time of those, and they are:

CTAO to YAK  05:54.6 minutes
CTAO to TIXI  06:51.6 minutes
YAK to TIXI 00:57.0 minutes

Then I went to my Excel database and looked for the times that
I have for previous quakes.

Here is what I have for CTAO to YAK:
                 Time    Lat.    Long.   Description
CTAO	YAK	00:34.8	3.7	90.0	OFF W COAST OF NORTHERN SUMATRA
CTAO	YAK	03:14.7	-6.1	104.1	SUNDA STRAIT
CTAO	YAK	04:11.0	1.3	126.3	NORTHERN MOLUCCA SEA
CTAO	YAK	05:40.8	-3.3	130.6	SERAM, INDONESIA
CTAO	YAK	05:48.3	-3.6	131.2	IRIAN JAYA REGION, INDONESIA
CTAO	YAK	06:16.1	-6.9	128.9	BANDA SEA
CTAO	YAK	07:26.0	-5.5	151.6	NEW BRITAIN REGION, P.N.G.
CTAO	YAK	07:34.5	-15.0	167.3	VANUATU ISLANDS
CTAO	YAK	07:56.3	-6.4	148.2	NEW BRITAIN REGION, P.N.G.

So, I would guess that this quake will fit in the area of the 3 listings
of 3.3S 130.6E, 3.6S 131.2E, and 6.9S 128.9E.

Now, the time difference between CTAO and TIXI:

CTAO	TIXI	00:13.6	22.8	125.6	SOUTHEAST OF TAIWAN
CTAO	TIXI	03:39.5	-4.6	102.8	SOUTHERN SUMATRA
CTAO	TIXI	04:20.0	5.2	126.0	MINDANAO, PHILIPPINES
CTAO	TIXI	04:41.0	3.8	126.2	TALAUD ISLANDS
CTAO	TIXI	05:09.2	1.6	126.3	NORTHERN MOLUCCA SEA
CTAO	TIXI	06:15.6	-2.9	128.2	CERAM SEA
CTAO	TIXI	06:38.9	-3.3	130.6	SERAM, INDONESIA
CTAO	TIXI	07:17.8	-4.5	133.8	IRIAN JAYA REGION, INDONESIA

The time for the "unknown" quake was 06:51.6, so it fits close to
2.9S 128E, 3.3S 130.6E, and 4.5S 133.8E.


Now the last time difference is YAK to TIXI:

YAK	TIXI	00:46.6	11.0	92.5	ANDAMAN ISLANDS, INDIA
YAK	TIXI	00:56.0	-6.8	128.7	BANDA SEA
YAK	TIXI	00:58.1	-3.3	130.6	SERAM, INDONESIA
YAK	TIXI	01:16.1	40.2	114.0	NORTHEASTERN CHINA

The YAK to TIXI time for the "unknown" quake is 00:57.0 which could
possibly fit all of the above, but considering the other two time
differences, I would say that this "unknown" quake was close to
3.3S 130E.

My spreadsheet also shows (I deleted for this example) the date
and time of the quake and a computed quake origination time.
Actually the origination time is the difference between the
P-wave arrival time of the first station listed and the actual
time as given my the NEIC.

I know this is not very accurate, but I have found it to be
fun to use.

If anyone would like the spreadsheet (Excel 5.0 format), please
e-mail me at:  jdcooley@.......  and request it.  DO NOT reply
to this message because it will go to the entire PSN mailing list!

Although I have put a LOT of work into this, there is no charge
for the database.  It is copyrighted, so please respect that.

BTW, instead of using AutoDRM you can get the information
from many stations by using Larry's web page:

http://psn.quake.net/bbrequest.html

That would be a good starting point (easier and faster), but
the stations you want may not be listed there.

"JD" Cooley
jdcooley@.......



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