Hi.

Sorry for the late reply.

The sensor is a L4 1Hz, i do have a noisy system due to several factors
(some already discussed here in PSN Listing Mail).

Here is the SAC file of the event:
http://dl.dropbox.com/u/15802004/12_10_2012.sac

This the SAC file of the IDA station located +-10km of the event (much
better recording than mine).
http://dl.dropbox.com/u/15802004/cmla_12_10_2012.sac

I do not know if this is a "natural" event, while i do receive some
"blasts" every month, at 4am i dont believe to be a blast.This event is
located near a dormat volcano, that 10 years back had high seismic crisis.
Some believe that the geothermal exploration on that system turned the
system a bit unstable ( coincidence when they started the exploration back
in the 80s, the area had a big seismic crisis). This event was classified
with Ml1.8, 5km depth.

So the hypothesis are:
-Only S wave was recorded, P wave is missed between the noise.
-Only P wave is clearly recorded.
-Due to short distance to the epicenter, P and S waves are mixed together.

But except this event and 1/2 more, i can always understand if a P is
recorded or not. Comparing my SAC file with the CMLA IDA station, what do
you think?

Best Regards,
Tiago.





2012/12/13 Bob Hancock 

> One other thought, the peak amplitudes of the P & S waves are 90 degrees
> out of phase.  Also the classification of the focal mechanism of the even=
t
> could have contributed to one wave being much more visible than the other
> wave.
>
> The amplitude of body waves such as the P & S waves, are dependent upon
> the focal mechanism of the event.
>
> Another factor is the sensitivity range or band width of your receiver.
>  If it is either a high frequency receiver or of minimal band width, you
> could see the P wave and the S wave would not be visible, whereas with a
> broader band receiver both waves would be visible.
>
> Your email does not define the scale at the bottom of the chart, minutes
> or seconds, but in either case no surface waves are visible.  Again this
> could be related to the frequency range of your receiver.
>
> Bob Hancock
>
>
> On Dec 12, 2012, at 4:20 PM, Tiago A.  wrote:
>
> Hi.
>
> Some months back i recorded a Ml1.8 event (epicenter at 22km), the P wave
> is perfectly noticed, but the S wave is somewhat lost.
>
> This is a picture of the earthquake (no filter applied)..i can get the sa=
c
> file if anyone is interested. A IDA station located more near from the
> epicenter also have this "issue" in this earthquake, clear P wave, S wave
> bit lost.
> http://imageshack.us/a/img252/2303/12102012.png
>
> I=B4ve this video from another event (Ml2.9) near that area, also doesnt
> have a clear S wave.
> https://www.youtube.com/watch?v=3Dj0P2y2ahDNg
>
> In the Ml1.8 event the lack of a clear S Wave is more evident, what
> happened to the S wave? This events occured near a volcanic region, but
> i=B4ve recorded earthquakes from other volcanic regions, and i have alway=
s a
> clear P, S wave.
>
> I apreciate any thought on this.
>
> Regards,
> Tiago.
>
>
>
Hi.

Sorry for the late reply.

The sensor is a L4 1Hz, i do ha=
ve a noisy system due to several factors (some already discussed here in PS=
N Listing Mail).

Here is the SAC file of the event:
http://dl.dropbox.com/u/1580=
2004/12_10_2012.sac


This the SAC file of the IDA station located +-10km of the event (much =
better recording than mine).
http://dl.dropbox.com/u/15802004/cmla_12_10_2012.sac<=
/a>


I do not know if this is a "natural" event, while i do receiv=
e some "blasts" every month, at 4am i dont believe to be a blast.=
This event is located near a dormat volcano, that 10 years back had high se=
ismic crisis. Some believe that the geothermal exploration on that system t=
urned the system a bit unstable ( coincidence when they started the explora=
tion back in the 80s, the area had a big seismic crisis). This event was cl=
assified with Ml1.8, 5km depth.


So the hypothesis are:
-Only S wave was recorded, P wave is missed b=
etween the noise.
-Only P wave is clearly recorded.
-Due to short dis=
tance to the epicenter, P and S waves are mixed together.

But except=
 this event and 1/2 more, i can always understand if a P is recorded or not=
.. Comparing my SAC file with the CMLA IDA station, what do you think?


Best Regards,
Tiago.





2012/12/13 Bob Hancock <raptor@.......>

One other thought, the peak amplit=
udes of the P & S waves are 90 degrees out of phase. =A0Also the classi=
fication of the focal mechanism of the event could have contributed to one =
wave being much more visible than the other wave. =A0

The amplitude of body waves such as the P & S waves=
, are dependent upon the focal mechanism of the event.

=
Another factor is the sensitivity range or band width of your receiver=
.. =A0If it is either a high frequency receiver or of minimal band width, yo=
u could see the P wave and the S wave would not be visible, whereas with a =
broader band receiver both waves would be visible. =A0

Your email does not define the scale at the bottom of t=
he chart, minutes or seconds, but in either case no surface waves are visib=
le. =A0Again this could be related to the frequency range of your receiver.=
=A0

Bob Hanc=
ock


=
On Dec 12, 2012, at 4:20 PM, Tiago A. <tiagoagre@.........> wrote:

Hi.

Some months back i recorded a Ml1.=
8 event (epicenter at 22km), the P wave is perfectly noticed, but the S wav=
e is somewhat lost. 

This is a picture of the earthquake (no filter =
applied)..i can get the sac file if anyone is interested. A IDA station loc=
ated more near from the epicenter also have this "issue" in this =
earthquake, clear P wave, S wave bit lost.


http://imageshack.us/a/img252/2303/12102012.png

I=B4ve this v=
ideo from another event (Ml2.9) near that area, also doesnt have a clear S =
wave.

https://www.youtube.com/watch?v=3Dj0P2y2ahDNg


In the Ml1.8 event the lack of a clear S Wave is more evident, what hap=
pened to the S wave? This events occured near a volcanic region, but i=B4ve=
 recorded earthquakes from other volcanic regions, and i have always a clea=
r P, S wave.



I apreciate any thought on this.

Regards,
Tiago.