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 =
event could have contributed to one wave being much more visible than =
the other wave. =20

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. =20

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.=20

Bob Hancock


On Dec 12, 2012, at 4:20 PM, Tiago A.  wrote:

> Hi.
>=20
> 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.=20
>=20
> This is a picture of the earthquake (no filter applied)..i can get the =
sac 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
>=20
> 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
>=20
> 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 =
always a clear P, S wave.
>=20
> I apreciate any thought on this.
>=20
> Regards,
> Tiago.

tiagoagre@.........> =
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 sac 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 =
always a clear P, S wave.


I apreciate any thought on this.

Regards,
Tiago.


=