Petra - I think Don's owes you a well-deserved pay-back
and
Cathryn - You can come out of the shallow end of the swimming pool now with
your head held high.

Well, folks, the "I'll Jump in contest" wasn't quite over after all.
You will recall back at the beginning of November Cathryn suggested
the epicenter of 37.1N 122W was due for an earthquake of Ml 3.5-4.5
and gave a time window from Nov. 1-10. That started a contest - other
entries were:
Lowell: within 50 km of 37.1N 122W Ml 2-5-3.5 between Nov. 7-11
Don : within 40 km of 37.2N 122W Ml 3.5-4.5 between Nov. 6-10
Roger : no such Event
Pam : Agreed with Cathryn

But then, tonight Petra jumped into the mix (after telling us in no
uncertain terms, she wasn't going to post any more forecasts - and
then taking a woman's perogative and changing her mind) and posted
the following forecast:

Petra : within 40 km of 37.3N 121.9W Ml 2.8-3.8 between Nov 15 at 9:17PST
and Nov 25 Midnight PST

Tonight there was a Ml 3.1 near Aptos, California with
the following NCSN parameters:

O: 16NOV2001 09:11:30 37.1N 121.9W ML=3.1 NCSN NE of Santa Cruz, CA

This event lies about 22 km from Petra's forecast and within the
magnitude and time windows (about 4 hours after her prediction was
posted). I sure would like to know how you did that Petra. Congratulations,
Petra, now it's time for Don to treat you!! Are you guys getting good or what!!

I posted probabilities on Petra's prediction in an earlier post
so they will not be repeated here. For Petra's forecast see:

http://www.earthwaves.org/wwwboard/messages/11008.html

This event is also less than 10 km away from the original epicenter
that Cathryn had predicted, an epicenter basically agreed to by
everyone except Roger. Lowell was the only one within the magnitude
range, although Don had suggested the quake would be on the low
side of the 3.5-4.5 range Cathryn had predicted.
We declared a tie when the time window ran out on this event, so
that will not change, but just how "good" was Cathryn's prediction
had she included a 16-day time window or Lowell's (which is
essentially the same as Don's) with a 10-day time window.

PROBABILITY:

In the past 5 years (Nov 1, 1996 to Nov 1, 2001) there have been
22 ten-day time windows which included at least one event of Ml>=3.0
in this region; in the same time there were 17 16-day time windows
containing an event of Ml>=3 within 40 km. A total of 114 16-day time
windows and 182 10-day time windows give probabilities of a
success in a 10-day window at Ml>=3 of 0.12 and in a 16-day time
window to 0.15. These translate to odds of 1 in 8 and 1 in 7 respectively.
This was the first event of Ml>=3 in the stated region since April
12, 2001 when a Ml 3.6 occurred near Hollister.
But getting the epicenter as close as Cathryn did was quite a different
matter. The epicenter is the first within 10 km with Ml>=3 since
a swarm between Dec 28-31, 1998 (nearly 3 years), and these were the
only such events in the past 10-years. No matter how you slice the
dice, the prediction of an unusual event at this epicenter at this
time was very difficult to accomplish by chance. Congratulations
Cathryn, all the rest of us (except Roger) were just bandwagoneers.

For Cathryn's original prediction see:

http://www.earthwaves.org/wwwboard/messages/10570.html

• Petra's earthquake Forecast for Aptos