https://wiki.seg.org/index.php?title=Effect_of_filtering_on_event_picking&feed=atom&action=historyEffect of filtering on event picking - Revision history2019-10-17T05:30:02ZRevision history for this page on the wikiMediaWiki 1.31.4https://wiki.seg.org/index.php?title=Effect_of_filtering_on_event_picking&diff=131490&oldid=prevAgeary: added page2019-05-20T14:13:16Z<p>added page</p>
<p><b>New page</b></p><div>{{publication<br />
| name = Problems in Exploration Seismology and their Solutions<br />
| image = [[File:897.Def.Lz-cropped.png|frameless|180px|link=Problems in Exploration Seismology and their Solutions]]<br />
| width = 120px<br />
| series = Geophysical References Series<br />
| title = [[Problems in Exploration Seismology and their Solutions]]<br />
| part = <br />
| chapter = 7<br />
| pages = 221 - 252<br />
| author = [[Lloyd P. Geldart]] and [[Robert E. Sheriff]]<br />
| doi = 10.1190/1.9781560801733<br />
| pdf = <br />
| store = https://shop.seg.org/shop/products/detail/897<br />
| isbn = ISBN 9781560801153<br />
}}<br />
== Problem ==<br />
Figure 7.13a shows changes in wave-shape produced by the analog filtering in modern digital instruments. What can you conclude about the effects on picking?<br />
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=== Solution ===<br />
The filtering on traces (b) and (c) is normal alias filtering for 2 ms and 4 ms sampling. Comparison of traces (a), (b), and (c) shows that lowering the high-frequency cut increases the delay. Comparing (c) and (d), we see that increasing the filter slope also increases the delay. Comparing traces (e) and (f) shows that changing the high-frequency slope changes the pulse shape but has little effect on the delay. Changing the low-frequency cut has a similar effect as seen by comparing (c) and (g). Narrowing the bandwidth results in shifting energy backward within the wavelet, decreasing the ability to pick early within the wavelet and increasing the likelihood of misinterpreting polarity.<br />
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[[file:ch07_fig7-13a.png|thumb|{{figure number|7.13a}} Far-field air-gun signals through various instrument filters: (a) no extra filtering; (b) out-24 Hz, 72 dB/octave; (c) out-62 Hz, 72 dB/octave; (d) out-62 Hz, 18 dB/octave; (e) 8–124 Hz with slopes of 18 and 72 dB/octave, respectively; (f) 18–124 Hz with 18 and 36 dB/octave slopes; (g) 8–62 Hz with 36 and 72 dB/octave slopes. Timing marks are 10 ms apart.]]<br />
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== Continue reading ==<br />
{| border="1" cellpadding="5" cellspacing="0" align="center"<br />
|-<br />
! style="background: #426580; color: white;" | Previous section<br />
! style="background: #E5D75F;" | Next section<br />
|-<br />
| align="center" | [[Filter effects on waveshape]]<br />
| align="center" | [[Binary numbers]]<br />
|-<br />
! style="background: #426580; color: white;" | Previous chapter<br />
! style="background: #E5D75F;" | Next chapter<br />
|-<br />
| align="center" | [[:Category: Characteristics of seismic events|Characteristics of seismic events]]<br />
| align="center" | [[:Category: Reflection field methods|Reflection field methods]]<br />
|-<br />
| align="center" colspan="2" |<br />
[[Problems_in_Exploration_Seismology_and_their_Solutions|Table of Contents (book)]]<br />
|}<br />
<br />
== Also in this chapter ==<br />
* [[Radiolocation errors because of velocity variations]]<br />
* [[Effect of station angle on location errors]]<br />
* [[Transit satellite navigation]]<br />
* [[Effective penetration of profiler sources]]<br />
* [[Directivity of linear sources]]<br />
* [[Sosie method]]<br />
* [[Energy from an air-gun array]]<br />
* [[Dominant frequencies of marine sources]]<br />
* [[Effect of coil inductance on geophone equation]]<br />
* [[Streamer feathering due to cross-currents]]<br />
* [[Filtering effect of geophones and amplifiers]]<br />
* [[Filter effects on waveshape]]<br />
* [[Effect of filtering on event picking]]<br />
* [[Binary numbers]]<br />
<br />
== External links ==<br />
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[[Category: Seismic equipment]]</div>Ageary