## PSN-L Email List Message

Subject: Vertical vs. Horz.
From: "Ted Channel" tchannel@............
Date: Tue, 22 Dec 2009 07:13:33 -0700

```Merry Christmas Folks,   I hope you all enjoy holidays.

I may have asked this question before, but need to ask it again.

I have recorded more earthquakes on vertical sensors then horizontal =
sensors.    Several different approaches for both, and a variety of =
periods, from 1 to 25 seconds.
My next sensor will be a vertical.   Before I begin I wanted to ask the =
following.

I know the 1.5 second vertical, will see the P and if the event is  =
large enough, it will see other phases.=20
Picture a free hanging spring with a mass.
My theory is the P wave stimulates the spring from an angle, a bit like =
An example would be if the earthquake occurred 180 degrees from the =

1  I know this is an over simplification, but does the  P arrives at an =
angle (bottom to top) and this influences the spring?   Yes, I have seen =
different explanations, wave simulator etc. but these did not answer the =
question.   If this is not the case can someone explain how the vertical =
spring is influenced.

The obvious advantage of a vertical is they see many earthquakes, the =
disavantage they are limited and also see a lot of other things which =
are not earthquakes.    All of my verticals have been 1 to 2.5 seconds.  =
This range has never seemed to be and advantage or disadvantage.   The =
2.5 second seemed to work no better then the 1 second.    I think this =
is because the sensor is just picking up the P (mainly) anyhow.
However on a big event it does show the P, the S and some other phases.  =
A typical vertical sensor recording will have a trace of  20 mins vs. a =
3 hours trace on the Lehman.

2.  If I could achieve a long period vertical, what would be the ideal =
target, if there is one?   An example the period target for a Lehman =
style is 20 seconds.

Before I being, I wanted to understand, if the longer period (vertical) =
would be any benefited.    I know I could create a vertical with 3 =
seconds.   I don't know if I could create one with 6 seconds.   If there =
is no advantage to the longer period in the Z axis, then it would serve =
no purpose.

One's location has an influence on which sensor type works for them.    =
I enjoy having both vertical and horz, shorter and longer periods.   In =
this case, I want to target a longer period vertical if the longer =
period would be better.

Merry Christmas Folks,   I =
hope you all=20
enjoy holidays.

I may have asked this question before, =
but need to=20

I have recorded more earthquakes on =
vertical=20
sensors then horizontal sensors.    Several different =
approaches=20
for both, and a variety of periods, from 1 to 25 seconds.
My next sensor will be a =
vertical.  =20
Before I begin I wanted to ask the following.

I know the 1.5 second =
vertical, will=20
see the P and if the event is  large enough, it will=20
see other phases.
Picture a free hanging spring with a=20
mass.
My theory is the P wave stimulates the =
spring from=20
an angle, a bit like its coming from your feet to your =
An example would be if the earthquake =
occurred 180=20
degrees from the sensor, the result would be directly from your feet to =
your=20

1  I know this is an over =
simplification,=20
but does the  P arrives at an angle (bottom to top) and this=20
influences the spring?   Yes, I have seen different =
explanations, wave=20
simulator etc. but these did not answer the question.   =
If this=20
is not the case can someone explain how the vertical spring is=20
influenced.

The obvious advantage of a vertical is =
they see=20
many earthquakes, the disavantage they are limited and also see a lot of =
other=20
things which are not earthquakes.    All of my verticals =
have=20
been 1 to 2.5 seconds.  This range has never seemed to be and =
disadvantage.   The 2.5 second seemed to work no better then =
the 1=20
second.    I think this is because the sensor is just =
picking up=20
the P (mainly) anyhow.
However on a big event it does show the =
P, the S=20
and some other phases.   A typical vertical sensor =
recording will=20
have a trace of  20 mins vs. a 3 hours trace on the =
Lehman.

2.  If I could achieve a long =
period vertical,=20
what would be the ideal target, if there is one?   An example =
the=20
period target for a Lehman style is 20 seconds.

Before I being, I wanted to understand, =
if the=20
longer period (vertical) would be any benefited.    I =
know I=20
could create a vertical with 3 seconds.   I don't know if I =
could=20
create one with 6 seconds.   If there is no advantage to the =
longer=20
period in the Z axis, then it would serve no purpose.

One's location has an influence on =
which sensor=20
type works for them.    I enjoy having both vertical and =
horz,=20
shorter and longer periods.   In this case, I want to target a =
longer=20
period vertical if the longer period would be better.

Thanks, Ted
```