This is an evaluation of an earthquake prediction Don in Shaky Town
made on June 12 for an event off the Coast of Oregon (#7591, June 12, 2001)

PNSN is reporting a 2.7 (PNSN ML) earthquake off the coast of Oregon
on July 3, 2001. The true magnitude is most likely about ML 4.2-4.5 according
to error analysis of past events in this region. Local time is
July 2, 2001 (7 hours earlier than UT time given by PNSN). This earthquake was registered
by 23 stations in the network. An event of ML>5 on May 11 was registered 29 stations,
whereas an event of 4.6 on May 20 was registered by only 8 recorders.

This is probably the largest event in the region since May 11
based on the number of reporting stations and stated PNSN magnitude.
As such it is a significant regional event.

See:
http://www.geophys.washington.edu/SEIS/PNSN/CATALOG_SEARCH/cat.search.html

To get this event and others off the Oregon coast, you must expand the
default latitude and longitude parameters. Be sure to include all events (M>0)
in an expanded range. Look for events with "R" as the second character - Regional events.

Our calculations, based on available seismograms gives an epicenter
for this event of 43.8N 127.7W with Mb 4.2-4.5. This is in keeping with
the known errors of PNSN for earthquake off the Coast of Oregon
(epicenters are ususally about 58-80 km too close to shore and
magnitudes are about 1.5 units smaller than actual for these events).
PNSN uses a local velocity model with spatially biased stations, so
errors are quite consistent.
Don had made a prediction to this board (#7591, June 12, 2001) which stated:

Earthquake Forecast Off Oregon Coast
Posted by Don in Hollister on June 12, 2001 at 13:43:01:

Magnitude: 4.5-6.0
From: 06/30/2001PDT - To: 07/05/2001PDT
Location: 225 miles west of Eugene, Oregon
Lat: 43.4N - Long: 127.7W - Range: 70Km

Hi All. My tummy is really acting up this morning so for right now I'm
looking at a 5.0Md+. The plus means that the maximum magnitude isn't that
well established and could be higher.

As to the geographic location the best I can do is 225 miles west of Eugene,
Oregon and maybe a tad bit south. The quake has the best chance of occurring
on 07/02/2001 at 43.4N/127.7W with a rough deviation of 70K north or south
and 30K east or west of the stated location.

My interest in forecasting a quake is not to gain a reputation of being able
to forecast a quake per say, but achieving an accurate forecast in regards
to location, time and magnitude. Let's just say I want to hit the bull's eye
on the side of the barn and not the barn itself. I realize that hitting the
bull's eye is almost impossible, but I don't want to use a radius that
would allow me to just hit the barn and be correct.

My training dictates to me that accuracy is paramount. It was instilled in me
many years ago and it is what I believe in.
Take Care...Don in creepy town.

EVALUATION

There are actually two predictions here, the specific prediction
for an event on July 2 and the general prediction in the header for
an event between 30 June and 5 July.

Comparing the specific prediction with the event:

Predicted: July 2, 2001 43.4N 127.7W Ml 4.5+ Off Coast of Oregon
Occurred : July 2, 2001 LT 43.8N 127.7W Ml 4.2-4.5 Off Coast of Oregon
PNSN loc : July 2, 2001 LT 44.0N 127.1W Ml 2.7+ Off Coast of Oregon

The estimated error was 70 km N/S. The error with PNSN epicenter
in N/S direction is 66 km and with revised location is 22 km. In
both cases the observed error is within the estimated error range.
The error in E/W location is 30 km. The error with PNSN epicenter
in E/W direction is 40 km and with revised location is 0 km. In
both cases the observed error is near or within the estimated error
range. PNSN is likely to have considerable error E/W and state
the location given is quality DC (within 100 km of true epicenter).
The date of the expected earthquake is exactly the same as the
local date of the occurring earthquake.
The expected Ml Magnitude is at the lower end of the magnitude
range given.
In all regards, this prediction is an exact (within stated
error parameters) match with the event occurrence. Prediction grade: A.

The general prediction was equally well done. The earthquake did
occur within the time span cited with estimated magnitude within
the lower range of given magnitudes. The distance from the expected
epicenter and the given epicenter (PNSN) is 74 km, with the revised
epicenter is 22 km. Both fall within or near the 70 km estimated
epicentral distance error. Prediction grade: A to A-

• PNSN Catalog data