{"id":398,"date":"2014-10-08T19:52:00","date_gmt":"2014-10-08T19:52:00","guid":{"rendered":"http:\/\/ahay.org\/blog\/?p=398"},"modified":"2015-08-29T15:53:09","modified_gmt":"2015-08-29T15:53:09","slug":"program-of-the-month-sfsigmoid","status":"publish","type":"post","link":"https:\/\/ahay.org\/blog\/2014\/10\/08\/program-of-the-month-sfsigmoid\/","title":{"rendered":"Program of the month: sfsigmoid"},"content":{"rendered":"<p><a href=\"\/RSF\/sfsigmoid.html\">sfsigmoid<\/a> generates a 2-D synthetic reflectivity model, created by <a href=\"http:\/\/sepwww.stanford.edu\/data\/media\/public\/sep\/prof\/index.html\">Jon Claerbout<\/a>.<\/p>\n<p><img decoding=\"async\" src=\"\/RSF\/book\/tccs\/flat\/flat\/Fig\/sigmoid.png\" alt=\"\" title=\"\" \/> <\/p>\n<p>One of the first occurrences of this model is in <a href=\"http:\/\/sepwww.stanford.edu\/data\/media\/public\/docs\/sep73\/toc_html\/index.html\">SEP-73<\/a> sponsor report from 1992, where it appeared in several papers:<\/p>\n<ul>\n<li>J. F. Claerbout, 1992, Introduction to Kirchhoff Migration Programs: SEP-73 report, 361-366, Stanford Exploration Project.<\/li>\n<li>J. F. Claerbout, 1992, Filling Data Gaps Using a Local Plane-Wave Model: SEP-73 report, 401-408, Stanford Exploration Project.<\/li>\n<li>J. F. Claerbout, 1992, Information from Smiles: Mono-Plane-Annihilator Weighted Regression: SEP-73 report, 409-420, Stanford Exploration Project.<\/li>\n<li>\n<p>J. F. Claerbout, 1992, Crossline Regridding by Inversion: SEP-73 report, 421-428, Stanford Exploration Project.<\/p>\n<p>The model was described as &#8220;a synthetic model that illustrates local variation in bedding. Notice dipping bedding, curved bedding, unconformity between them, and a fault in the curved bedding.&#8221; Later, the sigmoid model made an appearance in Claerbout&#8217;s book <em>Basic Earth Imaging<\/em>. The following example from <a href=\"\/RSF\/book\/bei\/krch\/sep73.html\">bei\/krch\/sep73 <\/a> illustrates the effect of aliasing on Kirchhoff modeling and migration:<\/p>\n<\/li>\n<\/ul>\n<p><img decoding=\"async\" src=\"\/RSF\/book\/bei\/krch\/sep73\/Fig\/skmod.png\" alt=\"\" title=\"\" \/> <\/p>\n<p>The model has appeared in numerous other tests. The following example from <a href=\"\/RSF\/book\/tccs\/flat\/flat.html\">tccs\/flat\/flat<\/a> shows automatic flattening of the sigmoid model by predictive painting. <\/p>\n<p><img decoding=\"async\" src=\"\/RSF\/book\/tccs\/flat\/flat\/Fig\/flat.png\" alt=\"\" title=\"\" \/><\/p>\n<p><strong>sfsigmoid<\/strong> has several parameters that control the model. The usual <strong>n1=<\/strong>, <strong>n2=<\/strong>, <strong>o1=<\/strong>, <strong>o2=<\/strong>, <strong>d1=<\/strong>, <strong>d2=<\/strong> parameters control the mesh size and sampling, <strong>taper=<\/strong> indicates whether to taper the sides of the model, <strong>large=<\/strong> controls the length of the synthetic reflectivity series. The program takes no input. <\/p>\n<h3 id=\"10previousprogramsofthemonth\">10 previous programs of the month:<\/h3>\n<ul>\n<li><a href=\"\/blog\/2014\/09\/24\/program-of-the-month-sfmax1\/\">sfmax1<\/a><\/li>\n<li><a href=\"\/blog\/2014\/08\/03\/program-of-the-month-sfstolt\/\">sfstolt<\/a><\/li>\n<li><a href=\"\/blog\/2014\/07\/13\/program-of-the-month-sfltft\/\">sfltft<\/a><\/li>\n<li><a href=\"\/blog\/2014\/06\/11\/program-of-the-month-sfeikonal\/\">sfeikonal<\/a><\/li>\n<li><a href=\"\/blog\/2014\/05\/13\/program-of-the-month-sfhelicon\/\">sfhelicon<\/a><\/li>\n<li><a href=\"\/blog\/2014\/04\/02\/program-of-the-month-sfcostaper\/\">sfcostaper<\/a><\/li>\n<li><a href=\"\/blog\/2014\/03\/11\/program-of-the-month-sflpad\/\">sflpad<\/a><\/li>\n<li><a href=\"\/blog\/2014\/02\/06\/program-of-the-month-sfdipfilter\/\">sfdipfilter<\/a><\/li>\n<li><a href=\"\/blog\/2014\/01\/09\/program-of-the-month-sfinttest1\/\">sfinttest1<\/a><\/li>\n<li><a href=\"\/blog\/2013\/12\/01\/program-of-the-month-sfcausint\/\">sfcausint<\/a><\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>sfsigmoid generates a 2-D synthetic reflectivity model, created by Jon Claerbout. One of the first occurrences of this model is in SEP-73 sponsor report from 1992, where it appeared in several papers: J. F. Claerbout, 1992, Introduction to Kirchhoff Migration Programs: SEP-73 report, 361-366, Stanford Exploration Project. J. F. Claerbout, 1992, Filling Data Gaps Using [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","activitypub_content_warning":"","activitypub_content_visibility":"","activitypub_max_image_attachments":4,"activitypub_interaction_policy_quote":"anyone","activitypub_status":"","footnotes":""},"categories":[3],"tags":[],"class_list":["post-398","post","type-post","status-publish","format-standard","hentry","category-programs"],"_links":{"self":[{"href":"https:\/\/ahay.org\/blog\/wp-json\/wp\/v2\/posts\/398","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ahay.org\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ahay.org\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ahay.org\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ahay.org\/blog\/wp-json\/wp\/v2\/comments?post=398"}],"version-history":[{"count":3,"href":"https:\/\/ahay.org\/blog\/wp-json\/wp\/v2\/posts\/398\/revisions"}],"predecessor-version":[{"id":13598,"href":"https:\/\/ahay.org\/blog\/wp-json\/wp\/v2\/posts\/398\/revisions\/13598"}],"wp:attachment":[{"href":"https:\/\/ahay.org\/blog\/wp-json\/wp\/v2\/media?parent=398"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ahay.org\/blog\/wp-json\/wp\/v2\/categories?post=398"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ahay.org\/blog\/wp-json\/wp\/v2\/tags?post=398"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}