PSN-L Email List Message

Subject: Ocean microseismic
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr@.........
Date: Fri, 08 May 2009 20:11:01 +0000

Hi all

I am decting ocean microseismic with my lehman seismometer according to
this web page.

A qoute from the web page.
"Microseisms are omnipresent energy recorded by seismometers over a
broad range of periods. Oceanic microseisms are a particularly energetic
type of microseisms occurring in the frequency band of 0.1=E2=80=931.0=E2=
=80=8AHz, and
usually dominated by wave periods of 5=E2=80=937=E2=80=8As, which are assoc=
iated with
high ocean waves of half their frequency. In a fundamental paper,
Longuet-Higgins (1950) showed that the corresponding ocean surface wave=E2=
wave interaction could, under suitable conditions, cause pressure
oscillations at double the frequency of the ocean waves, resulting in
seismic wave generation at the ocean floor. It was shown that at shallow
depths, where the propagation time of a compression wave from the ocean
surface to the bottom is small relative to the ocean wave period, the
compressibility of the water can be ignored, resulting in a simple
formulation of the pressure forcing function. This incompressible
formulation of the theory was verified in laboratory experiments on
periodic surface gravity waves by Cooper & Longuet-Higgins (1951), and
numerous studies have used the theory to confirm the causal relationship
between the ocean and the seismic waves that they generate at double
their frequencies."

The artical can be read here.

I live less then 800 meters from the ocean, so that signal is quite
strong on my sensor, as it peaks at 0.1Hz.

What I do wonder, will this have any effects on detecting earthquakes ?

J=C3=B3n Fr=C3=ADmann


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