Dear SANJAY For S minus P locationi you need to put 9 on weight column of p-phase line of the station with timing error. You can find info in SEISAN manual chapter 7 where location program HYP is described, i copy the lines below for your reference:
" Use of S-P and L-S differences: Uncertainty in absolute times often makes it necessary to be able to use the difference in time between two arrivals such as P and S or P and L. If no absolute times are available, the calculated origin time will be close to that at the first arrival station and is of course meaningless. However, a perfectly good epicenter and depth can still be obtained from P-S or P-L differences alone. To enable this feature, set the weight for the P phase input record to 9. This P is then assigned a weight of 0, effectively disabling its use. However, a time residual and azimuth, etc., will still be calculated for it, enabling an assessment to be made of its absolute time. A search will then be made of the entire input phase set for an S or L phase at the same station. If such a phase is found, its variables are used to store the observed and calculated difference times and their derivatives, and it’s weight (0-4) is used for the difference phase. DON’T SET IT TO 9!! If two or more such phases (e.g., SN, SG, LG, etc.) are found, all their differences with the P time will be used instead of their absolute times. Blanks will appear beneath ’hrmn’ in the residual summary for all such phases, while the observed and calculated difference times with the first P will appear beneath ’t-obs’ and ’t-cal’. " You may also see the event option 9 being used with station MOL for instance. Best regards, Mehmet È Kimden: "Sanjay Singh Negi" <[email protected]> Kime: "mehmetoz" <[email protected]> Kk: "p friberg" <[email protected]>, [email protected] Gönderilenler: 21 Şubat Cumartesi 2015 17:25:13 Konu: Re: [seisan] Station pick error Hello, Dear Paul and Mehmet I am glad to receive your responses. I would like to state that we are using taurus digitizer at each site. As I want to utilize this station anyhow please can you elaborate the idea using option 9 in s-file. As after your response I pinged and collected some details about the stations' state of health during 2012. The information I received explains that the GPS at ABI during the above mentioned period was not working and we are at loss with three months of data. The VSAT network was still sending the packets of data for this particular station. So for now I am with another query which may be a little bit silly but, can we synchronize the bad station time on the basis of already existing other stations time information. With Regards -- SANJAY SINGH NEGI Senior Research Fellow(SRF) Wadia Institute of Himalayan Geology 33 - GMS Road, Dehradun. Mob no.- +91-9536145596 ------------------------------------------------------------------------------------------------------------------------------------------------- ᐧ On Fri, Feb 20, 2015 at 9:51 PM, Yrd.Doc.Dr.Mehmet Ozyazicioglu < [email protected] > wrote: I agree with the possibility of GPS error , occasionally we also suffer from similar GPS faults in Turkey. In this case until you correct the GPS antenna or card, you can still use option 9 in s-file to locate using P minus s times Best regards, Mehmet Kimden: "Paul Friberg" < [email protected] > Kk: [email protected] Gönderilenler: 20 Şubat Cuma 2015 15:49:07 Konu: Re: [seisan] Station pick error Sanjay, If you are 100% certain about your P and S picks, and If the lat/lon of your station ABI is still correct, then it must be a timing issue. Your station ABI may be suffering a timing advance or lag problem. It is not unusual for modern digitizers to lose GPS lock and drift...but it seems pretty severe from the screenshots you showed. Could there be vegetation covering the GPS antenna or some other blockage. What flavor of digitizer is ABI running? Regards, Paul On Fri, Feb 20, 2015 at 8:11 AM, Sanjay Singh Negi < [email protected] > wrote: BQ_BEGIN Hi all, I have a continuous time series earthquake data from a small seismic network. All the stations were initially working very well. But in recent, after repairing one of the seismic station ABI, the P and S phase picks on this station shows very bad result. When I remove this station and consider others the result are of-course good, but I am not able to resolve why after introducing this station the errors abruptly increase. I am attaching the result of both, ABI station included and when not included. Kindly help me on this matter. Regards SANJAY SINGH NEGI Senior Research Fellow(SRF) Wadia Institute of Himalayan Geology 33 - GMS Road, Dehradun. Mob no.- +91-9536145596 _______________________________________________ seisan mailing list [email protected] http://mailman.uib.no/listinfo/seisan -- Paul Friberg ------------------- CEO/Seismologist ISTI == Instrumental Software Technologies, Inc. Geophysical Services and Software _______________________________________________ seisan mailing list [email protected] http://mailman.uib.no/listinfo/seisan _______________________________________________ seisan mailing list [email protected] http://mailman.uib.no/listinfo/seisan BQ_END
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