Hi Martin -

With two horizontal channels, you an use the amplitude of the P wave  
arrivals to determine a great circle path through your station.   
However that is insufficient information for you to determine which of  
two inbound headings the signal came from.  For that information, you  
need the initial motion on the P waves from both horizontal channels  
and the vertical channel.

Bob Hancock


On Mar 30, 2009, at 1:53 AM, Tangazazen@....... wrote:

> Hi Bob,
>
>   I was most interested in your surface wave comments.Here in  
> England local earth quakes are rare so most events detected are  
> teleseismic.
>
> I have a pendulum seismometer that resolves both X and Y axis  
> components independently ( broadband 50 seconds ). If I plot the N-S  
> verses E-W components during the first few minutes of a teleseismic  
> event one gets a form that indicates the direction of arrival. The  
> Svalbard event you mention shows a form whose major axis is along  
> the  NNW-SSE, consistent with it's location relative to England. For  
> the recent Tonga event M7.8, the X-Y plot has a majors axis  
> virtually north- south consistent with the shortest path though  
> China, Siberia and the north pole.
> Inspection of the individual seismographs show an initial strong  
> radial component relative to the transverse as would be expected.
>
> The last local event was  2 years ago ( M 4.7 ) so I have to make  
> the most of teleseismic events!
>
>
> Regards Martin

Hi Martin =
-

With two horizontal channels, you an use the =
amplitude of the P wave arrivals to determine a great circle path =
through your station.  However that is insufficient information for =
you to determine which of two inbound headings the signal came from. =
 For that information, you need the initial motion on the P waves =
from both horizontal channels and the vertical channel. =
 

Bob =
Hancock


On Mar 30, 2009, at 1:53 AM, =
Tangazazen@....... =
wrote:

 
 
Hi Bob,
 =
 
 
  I was most interested in your surface wave =
comments.Here in England local earth quakes are rare so most events =
detected are teleseismic.
 
 
 
I have a pendulum =
seismometer that resolves both X and Y axis components independently ( =
broadband 50 seconds ). If I plot the N-S verses E-W components =
during the first few minutes of a teleseismic event one gets a form that =
indicates the direction of arrival. The Svalbard event you mention shows =
a form whose major axis is along the  NNW-SSE, consistent with =
it's location relative to England. For the recent Tonga event =
M7.8, the X-Y plot has a majors axis virtually north- =
south consistent with the shortest path though China, Siberia and =
the north pole.
 
Inspection of the individual seismographs =
show an initial strong radial component relative to the transverse as =
would be expected.
 
 
 
The last local event =
was  2 years ago ( M 4.7 ) so I have to make the most of =
teleseismic events!
 
 
 
 
 =
Regards =
Martin  

=