Hi Chris

I have the understanding that if you have two horizontal channels, you  
will be able to determine a great circle path, but you will not know  
the direction the wave came inbound from.  For that you need to add  
the vertical channel.

At least that is how the computer program that John Lahr helped me put  
together many years ago works.  If you can do it with only two  
channels, I would be curious to see how it works.

Bob Hancock

On Sep 28, 2009, at 9:19 PM, ChrisAtUpw@....... wrote:

> In a message dated 29/09/2009, barry_lotz@............. writes:
> Geoff
> Along that line, a P wave being a pressure wave and a s wave being a  
> shear wave. It seems that if one could see two directions  
> simultaneously during an event one be able to combine the p wave  
> vectors and obtain the direction of max and min p wave contribution  
> and thus the approx direction of the event.
> Hi Barry,
>
>     The P wave comes up at quite a steep angle and it is rather  
> weak, so this is not such a good idea. But you have horizontal S  
> waves which carry the direction of propagation very well and are  
> usually much stronger. Two horizontal sensors should work fine.
>
>     Regards,
>
>     Chris Chapman

Hi Chris 

I have the understanding that if you have two horizontal channels, you will be able to determine a great circle path, but you will not know the direction the wave came inbound from.  For that you need to add the vertical channel.  

At least that is how the computer program that John Lahr helped me put together many years ago works.  If you can do it with only two channels, I would be curious to see how it works.

Bob Hancock

On Sep 28, 2009, at 9:19 PM, ChrisAtUpw@....... wrote:




In a message dated 29/09/2009, barry_lotz@............. writes:

  

    

    

      
Geoff
Along that line, a P wave being a pressure wave 
        and a s wave being a shear wave. It seems that if one could see two 
        directions simultaneously during an event one be able to combine the p 
        wave vectors and obtain the direction of max and min p wave contribution 
        and thus the approx direction of the 
event.

Hi Barry,
 
    The P wave comes up at quite a steep angle and it 
is rather weak, so this is not such a good idea. But you have horizontal S waves 
which carry the direction of propagation very well and are usually much 
stronger. Two horizontal sensors should work fine.
 
    Regards,
 
    Chris Chapman