PSN-L Email List Message

Subject: RE: Pis
From: "Stephen Hammond" shammon1@.............
Date: Tue, 21 Sep 2010 08:55:32 -0700


Hi Thomas, thanks for the reply. No harm no fault taken. I talked to
John some years back when he worked at the USGS site in Palo Alto and
the PSN had just been started. It was about 1990-91. I had recorded
several event files and in a few had seen a small wave before the
arrival of the initial P wave. It was really evident when there was very
low background noise. Like your records, most would be seen in events 30
miles or less. At the time, the PSN San Jose station was located in
South San Jose a few miles North of the split of the San Andreas and the
Calaveras faults. Located in a residential area with deep soils that had
once been farm land. Most of the events were South of my location along
the SA fault in Morgan Hill and Gilroy area. Just as now, every
seismograph I built seemed to have "its own issues" and this was also in
a time before any Internet time query sites or GPS's to keep accurate
time. So when John told me there was nothing before "P" I figured it was
just my equipment. Now that I have moved over to the Coast Range side of
the San Andreas and live 6km south of the Loma Prieta epicenter site, I
have not noticed them as I did in the old site. I do have a thought. By
chance, does your site align along the slip direction of any of these
events as mine did? 
Regards, Steve PSN San Jose, Aptos, CA

-----Original Message-----
From: psnlist-request@..............
[mailto:psnlist-request@............... On Behalf Of Thomas Dick
Sent: Monday, September 20, 2010 7:09 PM
To: psnlist@..............
Subject: Re: Pis


Steve, Please don't take me wrong -- I am not arguing and I certainly 
don't have the educational background or equipment of the calibre of 
most like you and John...this all started with WinQuake. I took the 
9/15/10 New Madrid quake of  9:37:17.9@... degrees and 9/19/10 
Arcadia-Oklahoma city, OK quake of 22:03:48.6 @... degrees via Vase, I 
compared them to USIN 30 miles west of me and "something" is there.I 
even "see" something on the 4.5hz vertical geophone which I rate as low 
novice quality for the New Madrid as well as Oklahoma quake.

Stephen Hammond wrote:
> I once asked John Lahr this same question and he told me there was 
> nothing before the P wave. I asked because I would see something 
> before P in events that were south of me in Morgan Hill and Gilroy 
> when my station was in South San Jose. Regards, Steve Hammond PSN San 
> Jose, Aptos, CA
>
> -----Original Message-----
> From: psnlist-request@.............. 
> [mailto:psnlist-request@...............
> On Behalf Of Thomas Dick
> Sent: Sunday, September 19, 2010 7:44 PM
> To: psnlist@..............
> Subject: Re: Pis
>
> Is there a reference where I can find a discussion of this subject. I
> figured it was some sort of reflected wave. John did you send
something?
>
> John Cole wrote:
>   
>> ---------------------------------------------------------------------
>> ---
>> *From:* Geoffrey 
>> *To:* psnlist@..............
>> *Sent:* Sat, September 18, 2010 10:41:22 PM
>> *Subject:* Re: Pis
>>
>> To Me it is a P wave which strikes the Inner Core then is reflected 
>> as
>> an S wave but that's kind of
>> ridiculous to think about since the outer core is liquid and No S 
>> waves can travel
>> through liquids.
>> An S wave in the inner core will go round in there until it dampens
to 
>> nothing.
>>
>> --------------------------------------------------
>> From: "Thomas Dick" > >
>> Sent: Monday, September 13, 2010 12:07 AM
>> To: >
>> Subject: Pis
>>
>>     
>>> Using Winquake, particularly on regional events, the vertical and
>>>       
>> broadside Lehman show a peak well ahead of P which it designates as
>> Pis. I can't find a reference to it. Is this some old designation for

>> a core or mantle reflection? 
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>
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>   

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