## PSN-L Email List Message

Subject: RE: M6.3 5327km from Sea Ranch, CA USA, NEAR E COAST OF KORYAKIA, RUSSIA
From: "Bob Hancock" carpediem1@.........
Date: Mon, 22 May 2006 14:04:21 -0700

```Hi All -

There are multiple formulas used to determine magnitude.  The magnitudes
determined by Harvard and NEIC often do not match and according to John
Lahr, the "Official" magnitude of an event is the greater of either Harvard
or NEIC.  Maybe John Lahr would comment on the magnitudes derived from other
sources such as the European-Mediterranean Seismic Center (EMSC) and how
they affect the "Official" magnitude of an event.

On the first event the magnitudes were:

6.7 - EMSC; 6.6 - Harvard; and 6.5 NEIC

On the second event the magnitudes were

6.1 - EMSC; 6.2 - Harvard; and 6.2 NEIC

Using the extremes 6.7 and 6.1 the seismic wave amplitude of the second
event would be 0.251 of the first event, and the radiated seismic energy
would be 0.125 of the first event.

Using the NEIC numbers 6.6 and 6.2, the seismic wave amplitude of the second
event would be 0.251 of the first event, and the radiated seismic energy
would be 0.251 of the first event.

Add to this the fact that the first event was shallow at 11.1 km, while the
second event was deep at 189.4 km - the depth would reduce the effects of
the Love and Rayleigh waves.

Another factor would be the natural seismic noise that would be present with
a location 3.14 miles from the ocean.  The event would have to be greater
than the lowest level of detection, a factor of the seismometer sensitivity
and background noise.

The formulas for computing the difference follow:

FM = First Magnitude
SM = Second Magnitude

M1A = 10 ^ FM
M1B = 10 ^ SM

Seismic Wave Amplitude Diff = M1B / M1A

Radiated Seismic Energy Diff = 10 ^ ((SM - FM) * 1.5)

Thanks to John Lahr for his help in putting these formulas together.

Bob Hancock
Three Points, AZ

-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@............... On
Behalf Of George Bush
Sent: Monday, May 22, 2006 10:52
To: Recipient list suppressed :
Subject: M6.3 5327km from Sea Ranch, CA USA, NEAR E COAST OF KORYAKIA,
RUSSIA

I recieved a nice strong signal fron this event. It is interesting that it
was followed by a M6.2 about two hours later just down the Kamchatka
pennensula and I didn't detect a thing???

USGS reports:

A magnitude 6.3 earthquake NEAR THE E COAST OF KORYAKIA, RUSSIA has
occurred at:
60.75N 165.88E  Depth  14km  Mon May 22 11:11:59 2006 UTC

Time: Universal Time         (UTC) Mon May 22 11:11:59 2006
Time Near Epicenter          Tue May 23 00:11:59 2006
Eastern Daylight Time  (EDT) Mon May 22 07:11:59 2006
Central Daylight Time  (CDT) Mon May 22 06:11:59 2006
Mountain Daylight Time (MDT) Mon May 22 05:11:59 2006
Pacific Daylight Time  (PDT) Mon May 22 04:11:59 2006
Hawaii Standard Time   (HST) Mon May 22 01:11:59 2006

Location with respect to nearby cities:
130 km (80 miles) NE of Il'pyrskiy, Russia (pop N/A)
620 km (385 miles) N of Nikol'skoye, Komandorskiye Ostrova, Rus.
740 km (460 miles) WSW of Anadyr', Russia
6330 km (3930 miles) NNE of MOSCOW, Russia

http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/usnaap.php .

You can go to http://psn.quake.net/cgi-dos/event.exe and see my recordings
by clicking on "(GIF Image)" for the event files from Sea Ranch.

George
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