## PSN-L Email List Message

Subject: Re: earthquake p and s wave fracturing ?
From: ChrisAtUpw@.......
Date: Mon, 20 Feb 2006 07:07:55 EST

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In a message dated 20/02/2006, jonfr500@......... writes:

This  earthquake has an energy component down to 2Hz and down to 1Hz, however
i just  don't record that frequency (1Hz) that low good with my geophone.
There also  appears to be some type of a fraction in the earthquake p and s
waves. It  appears more in the p wave, but is also visible in the s wave.

HI Jon,

From the distance, this looks like a near regional  quake. Your geophone
will see ~1/20 sensitivity at 1 Hz, 1/5 sensitivity at 2  Hz. If the waves are
strong enough you can see them. You may also see two sets  of P & S waves
which have travelled by different paths. There is a  discontinuity called the
Moho about 35 km down under land, 10 km down under  the sea. The volcanic
structures may interfere.

Regards,

Chris Chapman

In a message dated 20/02/2006, jonfr500@......... writes:
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>This=20
earthquake has an energy component down to 2Hz and down to 1Hz, however i=20=
just=20
don't record that frequency (1Hz) that low good with my geophone. There al=
so=20
appears to be some type of a fraction in the earthquake p and s waves. It=20
appears more in the p wave, but is also visible in the s wave.=20

HI Jon,

From the distance, this looks like a near regio=
nal=20
quake. Your geophone will see ~1/20 sensitivity at 1 Hz, 1/5 sensitivity at=20=
2=20
Hz. If the waves are strong enough you can see them. You may also see two se=
ts=20
of P & S waves which have travelled by different paths. There is a=20
discontinuity called the Moho about 35 km down under land, 10 km down u=
nder=20
the sea. The volcanic structures may interfere.

Regards,

Chris Chapman
```