{"id":72,"date":"2015-05-13T21:11:42","date_gmt":"2015-05-13T21:11:42","guid":{"rendered":"https:\/\/tungsten2.gps.caltech.edu\/?page_id=72"},"modified":"2025-09-22T15:09:24","modified_gmt":"2025-09-22T22:09:24","slug":"eqprocessing","status":"publish","type":"page","link":"https:\/\/www.scsn.org\/index.php\/seismologists-tools\/eqprocessing\/","title":{"rendered":"Earthquake Processing"},"content":{"rendered":"<p>Data from the seismic stations are telemetered and automatically processed in real-time by computers at Caltech and USGS in Pasadena. An overview of the steps from ground shaking to earthquake catalog is given below; if you need more details than are available on this website please check <a href=\"http:\/\/scedc.caltech.edu\/\" target=\"_blank\" rel=\"noopener noreferrer\">SCEDC<\/a> or <a href=\"\/index.php\/contact\/contact-us-2\/\">Contact Us<\/a>.<\/p>\n<div class=\"wonderpluginslider-container\" id=\"wonderpluginslider-container-3\" style=\"max-width:100%;margin:0 auto;padding-left:0px;padding-right:0px;padding-top:0px;padding-bottom:180px;\"><div class=\"wonderpluginslider\" id=\"wonderpluginslider-3\" data-sliderid=\"3\" data-width=\"900\" data-height=\"600\" data-skin=\"showcase\" data-autoplay=\"false\" data-randomplay=\"false\" data-loadimageondemand=\"true\" data-autoplayvideo=\"false\" data-isresponsive=\"true\" data-fullwidth=\"true\" data-isfullscreen=\"false\" data-showtext=\"true\" data-showtimer=\"false\" data-showbottomshadow=\"false\" data-navshowpreview=\"false\" data-textautohide=\"false\" data-lightboxresponsive=\"true\" data-lightboxshownavigation=\"false\" data-lightboxshowtitle=\"true\" data-lightboxshowdescription=\"false\" data-scalemode=\"fit\" data-arrowstyle=\"mouseover\" data-transition=\"slide\" data-loop=\"0\" data-border=\"0\" data-slideinterval=\"8000\" data-arrowimage=\"arrows-48-48-3.png\" data-arrowwidth=\"48\" data-arrowheight=\"48\" data-arrowtop=\"50\" data-arrowmargin=\"8\" data-navstyle=\"bullets\" data-navimage=\"bullet-24-24-5.png\" data-navwidth=\"24\" data-navheight=\"24\" data-navspacing=\"6\" data-navmarginx=\"12\" data-navmarginy=\"12\" data-playvideoimage=\"playvideo-64-64-0.png\" data-playvideoimagewidth=\"64\" data-playvideoimageheight=\"64\" data-lightboxthumbwidth=\"45\" data-lightboxthumbheight=\"30\" data-lightboxthumbtopmargin=\"12\" data-lightboxthumbbottommargin=\"4\" data-lightboxbarheight=\"64\" data-lightboxtitlebottomcss=\"{color:#333; font-size:14px; font-family:Armata,sans-serif,Arial; overflow:hidden; text-align:left;}\" data-lightboxdescriptionbottomcss=\"{color:#333; font-size:12px; font-family:Arial,Helvetica,sans-serif; overflow:hidden; text-align:left; margin:4px 0px 0px; padding: 0px;}\" data-textformat=\"Underneath center\" data-textpositionstatic=\"bottomoutside\" data-textpositiondynamic=\"bottomleft\" data-paddingleft=\"0\" data-paddingright=\"0\" data-paddingtop=\"0\" data-paddingbottom=\"180\" data-textcss=\"display:block; padding:12px 0px; text-align:center; margin-top:4px;\" data-textbgcss=\"display:none;\" data-titlecss=\"display:block; position:relative; font-size: 24px; font-weight: 600; font-family: Arial, Helvetica, sans-serif; color:#005851;\" data-descriptioncss=\"display:block; position:relative; font-size: 14px; font-family: Arial, Helvetica, sans-serif; color:#616265; margin-top:8px;\" data-jsfolder=\"https:\/\/www.scsn.org\/wp-content\/plugins\/wonderplugin-slider\/engine\/\" style=\"display:none;\" ><ul class=\"amazingslider-slides\" style=\"display:none;\"><li><img decoding=\"async\" class=\"amazingsliderimg\" src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step1.jpg\" alt=\"Data Transfer\" title=\"Data Transfer\" data-description=\"Ground motion data are sent continuously from the field site to the processing centers in small data packets. (Image: Seismic Instrumentation)\" \/><\/li><li><img class=\"amazingsliderimg\" data-src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step2.jpg\" alt=\"Waveform Storage\" title=\"Waveform Storage\" data-description=\"All incoming waveform data are archived. (Image: Data Servers)\" \/><\/li><li><img class=\"amazingsliderimg\" data-src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step3.jpg\" alt=\"Event Detection\" title=\"Event Detection\" data-description=\"Incoming data are scanned for events using a simple amplitude ratio method. If an amplitude increase above our set threshold is detected, a \u2018trigger\u2019 message is created. (Image: Continuous data stream from stations)\" \/><\/li><li><img class=\"amazingsliderimg\" data-src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step4.jpg\" alt=\"Event Association\" title=\"Event Association\" data-description=\"The system tries to associate \u2018triggers\u2019 to find real earthquakes. Triggers can be generated by any kind of environmental or system noise, so we set criteria to determine whether it is likely that a real earthquake has occurred. If the system detects enough triggers to suggest an earthquake it goes on to further processing. (Image: Map of subnets used to associate &#39;triggers&#39;)\" \/><\/li><li><img class=\"amazingsliderimg\" data-src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step5.jpg\" alt=\"Location\" title=\"Location\" data-description=\"The system uses the HypoInverse algorithm to determine earthquake location. This takes travel time information and solves for the 3D location and origin time of the event. The algorithm uses a simplified earth model: a 1D velocity model and station correction terms. (Image: Subsurface models of S. California from 1996)\" \/><\/li><li><img class=\"amazingsliderimg\" data-src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step6.jpg\" alt=\"Magnitude\" title=\"Magnitude\" data-description=\"Recorded amplitude information is used to determine earthquake magnitude. A number of different magnitude scales and calculation methods are possible (see our <a href=&quot;http:\/\/tungsten2.gps.caltech.edu\/index.php\/education-outreach-2\/faq\/#SCSNmag&quot; target=&quot;_blank&quot;>FAQ<\/a> &amp; <a href=&quot;http:\/\/www.usgs.gov\/faq\/categories\/9828\/3357&quot; target=&quot;_blank&quot;>USGS<\/a> for further explanations of magnitude scales). SCSN regularly determines Ml (local magnitude) for all events and Mw (moment magnitude) for larger events. (Image: Charles Richter)\" \/><\/li><li><img class=\"amazingsliderimg\" data-src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step7.jpg\" alt=\"Focal Mechanism &amp; Moment Tensor\" title=\"Focal Mechanism &amp; Moment Tensor\" data-description=\"Focal mechanisms and moment tensors are descriptions of the way the ground moved during an earthquake and are used by seismologists to understand faults (position and movements) and local stresses (for more information <a href=&quot;http:\/\/tungsten2.gps.caltech.edu\/index.php\/education-outreach-2\/faq\/#beachball&quot; target=&quot;_blank&quot;>Click Here<\/a>). SCSN calculates these types of solutions from the polarity (up or downwards motion) and amplitude measurements (focal mechanisms, using the HASH algorithm) or by fitting the waveforms (moment tensors, using the TMTS algorithm) when sufficient data are available. (Image: Moment Tensor solution)\" \/><\/li><li><img class=\"amazingsliderimg\" data-src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step8.jpg\" alt=\"Manual QC\" title=\"Manual QC\" data-description=\"Automated processing systems are necessary to deal with the large numbers of earthquakes recorded every day in southern California, however they don\u2019t always do a perfect job. SCSN has seismic analysts who check the automatic results and if required improve the results by manually reprocessing the data. (Image: Post processing auto analysis vs human analysis)\" \/><\/li><li><img class=\"amazingsliderimg\" data-src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step9.jpg\" alt=\"Results Distribution\" title=\"Results Distribution\" data-description=\"Once an earthquake has been processed, an automatic message is sent to partner organizations such as USGS and SCEDC where results are available in real-time. Updates and cancellations are also automatically sent out when a seismologist or analyst has reviewed and updated the result. (Image: Western U.S.  compiled earthquakes)\" \/><\/li><li><img class=\"amazingsliderimg\" data-src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step10.jpg\" alt=\"<a id=&quot;eqprocslider&quot; href=&quot;#catalog&quot;>Earthquake Catalogs<\/a>\" title=\"<a id=&quot;eqprocslider&quot; href=&quot;#catalog&quot;>Earthquake Catalogs<\/a>\" data-description=\"All earthquake results are stored in catalogs, available through <a href=&quot;http:\/\/scedc.caltech.edu\/eq-catalogs\/&quot;>SCEDC<\/a>. <a href=&quot;#catalog&quot;>Click Here<\/a> for more detail on earthquake catalogs, and <a href=&quot;http:\/\/tungsten2.gps.caltech.edu\/index.php\/seismologists-tools\/eqprocessing\/scsn-catalog-status\/&quot;>Here<\/a> for a history of the SCSN catalogue. (Image: SCEDC catalog search)\" \/><\/li><\/ul><ul class=\"amazingslider-thumbnails\" style=\"display:none;\"><li><img decoding=\"async\" class=\"amazingsliderthumbnailimg\" src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step1.jpg\" alt=\"Data Transfer\" title=\"Data Transfer\" data-description=\"Ground motion data are sent continuously from the field site to the processing centers in small data packets. (Image: Seismic Instrumentation)\" \/><\/li><li><img decoding=\"async\" class=\"amazingsliderthumbnailimg\" src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step2.jpg\" alt=\"Waveform Storage\" title=\"Waveform Storage\" data-description=\"All incoming waveform data are archived. (Image: Data Servers)\" \/><\/li><li><img decoding=\"async\" class=\"amazingsliderthumbnailimg\" src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step3.jpg\" alt=\"Event Detection\" title=\"Event Detection\" data-description=\"Incoming data are scanned for events using a simple amplitude ratio method. If an amplitude increase above our set threshold is detected, a \u2018trigger\u2019 message is created. (Image: Continuous data stream from stations)\" \/><\/li><li><img decoding=\"async\" class=\"amazingsliderthumbnailimg\" src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step4.jpg\" alt=\"Event Association\" title=\"Event Association\" data-description=\"The system tries to associate \u2018triggers\u2019 to find real earthquakes. Triggers can be generated by any kind of environmental or system noise, so we set criteria to determine whether it is likely that a real earthquake has occurred. If the system detects enough triggers to suggest an earthquake it goes on to further processing. (Image: Map of subnets used to associate &#39;triggers&#39;)\" \/><\/li><li><img decoding=\"async\" class=\"amazingsliderthumbnailimg\" src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step5.jpg\" alt=\"Location\" title=\"Location\" data-description=\"The system uses the HypoInverse algorithm to determine earthquake location. This takes travel time information and solves for the 3D location and origin time of the event. The algorithm uses a simplified earth model: a 1D velocity model and station correction terms. (Image: Subsurface models of S. California from 1996)\" \/><\/li><li><img decoding=\"async\" class=\"amazingsliderthumbnailimg\" src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step6.jpg\" alt=\"Magnitude\" title=\"Magnitude\" data-description=\"Recorded amplitude information is used to determine earthquake magnitude. A number of different magnitude scales and calculation methods are possible (see our <a href=&quot;http:\/\/tungsten2.gps.caltech.edu\/index.php\/education-outreach-2\/faq\/#SCSNmag&quot; target=&quot;_blank&quot;>FAQ<\/a> &amp; <a href=&quot;http:\/\/www.usgs.gov\/faq\/categories\/9828\/3357&quot; target=&quot;_blank&quot;>USGS<\/a> for further explanations of magnitude scales). SCSN regularly determines Ml (local magnitude) for all events and Mw (moment magnitude) for larger events. (Image: Charles Richter)\" \/><\/li><li><img decoding=\"async\" class=\"amazingsliderthumbnailimg\" src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step7.jpg\" alt=\"Focal Mechanism &amp; Moment Tensor\" title=\"Focal Mechanism &amp; Moment Tensor\" data-description=\"Focal mechanisms and moment tensors are descriptions of the way the ground moved during an earthquake and are used by seismologists to understand faults (position and movements) and local stresses (for more information <a href=&quot;http:\/\/tungsten2.gps.caltech.edu\/index.php\/education-outreach-2\/faq\/#beachball&quot; target=&quot;_blank&quot;>Click Here<\/a>). SCSN calculates these types of solutions from the polarity (up or downwards motion) and amplitude measurements (focal mechanisms, using the HASH algorithm) or by fitting the waveforms (moment tensors, using the TMTS algorithm) when sufficient data are available. (Image: Moment Tensor solution)\" \/><\/li><li><img decoding=\"async\" class=\"amazingsliderthumbnailimg\" src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step8.jpg\" alt=\"Manual QC\" title=\"Manual QC\" data-description=\"Automated processing systems are necessary to deal with the large numbers of earthquakes recorded every day in southern California, however they don\u2019t always do a perfect job. SCSN has seismic analysts who check the automatic results and if required improve the results by manually reprocessing the data. (Image: Post processing auto analysis vs human analysis)\" \/><\/li><li><img decoding=\"async\" class=\"amazingsliderthumbnailimg\" src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step9.jpg\" alt=\"Results Distribution\" title=\"Results Distribution\" data-description=\"Once an earthquake has been processed, an automatic message is sent to partner organizations such as USGS and SCEDC where results are available in real-time. Updates and cancellations are also automatically sent out when a seismologist or analyst has reviewed and updated the result. (Image: Western U.S.  compiled earthquakes)\" \/><\/li><li><img decoding=\"async\" class=\"amazingsliderthumbnailimg\" src=\"http:\/\/tungsten2.gps.caltech.edu\/wp-content\/uploads\/Seis tools steps\/step10.jpg\" alt=\"<a id=&quot;eqprocslider&quot; href=&quot;#catalog&quot;>Earthquake Catalogs<\/a>\" title=\"<a id=&quot;eqprocslider&quot; href=&quot;#catalog&quot;>Earthquake Catalogs<\/a>\" data-description=\"All earthquake results are stored in catalogs, available through <a href=&quot;http:\/\/scedc.caltech.edu\/eq-catalogs\/&quot;>SCEDC<\/a>. <a href=&quot;#catalog&quot;>Click Here<\/a> for more detail on earthquake catalogs, and <a href=&quot;http:\/\/tungsten2.gps.caltech.edu\/index.php\/seismologists-tools\/eqprocessing\/scsn-catalog-status\/&quot;>Here<\/a> for a history of the SCSN catalogue. (Image: SCEDC catalog search)\" \/><\/li><\/ul><div class=\"wonderplugin-engine\"><a href=\"http:\/\/www.wonderplugin.com\/wordpress-slider\/\" title=\"WordPress Image Slideshow\">WordPress Image Slideshow<\/a><\/div><\/div><\/div>\n<hr \/>\n<h5>Event Detection<\/h5>\n<p>As the energy from a propagating earthquake rolls across the sensors of our network, phase picks are automatically made on the approaching wave-front. These picks are then sent to the Event Associator to see if they can be processed into an earthquake.<\/p>\n<hr \/>\n<h5>Event Association<\/h5>\n<p>Algorithms designed to distinguish the characteristics of an earthquake run through the picks, often multiple times, in order to fit them together into\u00a0a reasonable solution, when it does; an earthquake is declared.<\/p>\n<hr \/>\n<h5>Location<\/h5>\n<p>Using station locations, phase arrival times\u00a0and the time delay between the P and S waves, the location program, Hypoinverse2000, quickly determines the earthquake&#8217;s source of origin.<\/p>\n<hr \/>\n<h5>Magnitude<\/h5>\n<p>Using the peak amplitudes measured from the earthquake&#8217;s waveforms along with\u00a0the earthquake&#8217;s location, a magnitude could soon be calculated and assigned.<\/p>\n<hr \/>\n<h5>Focal Mechanism &amp; Moment Tensor<\/h5>\n<p>Both the Focal Mechanisn and the Moment Tensor are both geometrical and\u00a0mathematical representations of the movement on a fault during an earthquake. Often referred to as \u201cbeach ball\u201d diagrams, they describe\u00a0the fault\u2019s orientation and direction of slip.<\/p>\n<hr \/>\n<h5>Results Distribution<\/h5>\n<p>Real-time information distribution is an integral part of SCSN operations. Twitter, paging, email, web, CISN display and alarm distribution are all part of how we disseminate information in real-time. Critical users of the information include utility companies, offices of emergency services\/management, other seismic networks, and media outlets and we work closely with these agencies to ensure they have the information they need. The general public is also a primary target of the real-time earthquake information distribution, and SCSN offers a variety of methods for the general public to receive earthquake information in near real-time.<\/p>\n<hr \/>\n<h5 id=\"catalog\">Earthquake Catalogs<\/h5>\n<p>The Caltech Seismological Laboratory, the USGS, and the Southern California Earthquake Data Center (SCEDC) have been working toward compiling and converting all available historic seismic data holdings to create a single-source for online access to southern California earthquake data. The SCEDC\u2019s database now contains all of the supporting data for southern California earthquakes from 1932 to the present. <a href=\"\/index.php\/seismologists-tools\/eqprocessing\/scsn-catalog-status\/\">Click Here<\/a> for a history of the catalog.<\/p>\n<p>The earthquake catalog information available at <a href=\"http:\/\/scedc.caltech.edu\/eq-catalogs\/\" target=\"_blank\" rel=\"noopener noreferrer\">SCEDC<\/a> provides a one-line summary of events\u2019 parameters and provides fundamental earthquake information including the event\u2019s date and time, location (latitude, longitude and depth), magnitude and the event\u2019s reference identification number (EVID). The catalog can also be searched using the same parameters.<\/p>\n<p>Users interested in accessing the more detailed earthquake information that is used to develop the catalog e.g., phase-picks, waveforms, station information etc., can access this data from the Data Center\u2019s STP (Seismic Transfer Program) program. STP is a client-side program for retrieving triggered and continuous waveform and phase data from the Southern California Earthquake Data Center.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Data from the seismic stations are telemetered and automatically processed in real-time by computers at Caltech and USGS in Pasadena. An overview of the steps from ground shaking to earthquake catalog is given below; if you need more details than<span class=\"ellipsis\">&hellip;<\/span><\/p>\n<div class=\"read-more\"><a href=\"https:\/\/www.scsn.org\/index.php\/seismologists-tools\/eqprocessing\/\">Read more &#8250;<\/a><\/div>\n<p><!-- end of .read-more --><\/p>\n","protected":false},"author":2,"featured_media":0,"parent":36,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"responsive\/sidebar-content-page.php","meta":{"footnotes":""},"class_list":["post-72","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.scsn.org\/index.php\/wp-json\/wp\/v2\/pages\/72","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.scsn.org\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.scsn.org\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.scsn.org\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.scsn.org\/index.php\/wp-json\/wp\/v2\/comments?post=72"}],"version-history":[{"count":30,"href":"https:\/\/www.scsn.org\/index.php\/wp-json\/wp\/v2\/pages\/72\/revisions"}],"predecessor-version":[{"id":5419,"href":"https:\/\/www.scsn.org\/index.php\/wp-json\/wp\/v2\/pages\/72\/revisions\/5419"}],"up":[{"embeddable":true,"href":"https:\/\/www.scsn.org\/index.php\/wp-json\/wp\/v2\/pages\/36"}],"wp:attachment":[{"href":"https:\/\/www.scsn.org\/index.php\/wp-json\/wp\/v2\/media?parent=72"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}