{"id":3576,"date":"2016-01-21T11:43:41","date_gmt":"2016-01-21T19:43:41","guid":{"rendered":"http:\/\/earthjay.com\/?p=3576"},"modified":"2016-01-21T11:43:41","modified_gmt":"2016-01-21T19:43:41","slug":"earthquake-report-rivera-fracture-zone-mexico","status":"publish","type":"post","link":"https:\/\/earthjay.com\/?p=3576","title":{"rendered":"Earthquake Report: Rivera fracture zone, Mexico!"},"content":{"rendered":"<p>We just had an earthquake offshore of Colima, Mexico. This earthquake appears associated with the Rivera fracture zone (RFZ), a transform plate boundary separating the Rivera plate to the north and the Pacific plate to the south. The RFZ connects segments of the East Pacific Rise, the oceanic spreading center where the Pacific plate, Rivera plate, and Cocos plate are formed. The RFZ is a system of stepped right lateral strike-slip faults. There is likely zero risk of a tsunami from this strike-slip earthquake. Here is the <a href=\"http:\/\/earthquake.usgs.gov\/earthquakes\/eventpage\/us10004g4l#general_summary\" target=\"_blank\" rel=\"noopener\">USGS web site for this earthquake<\/a>.<br \/>\nBelow is a map showing the regional tectonics. I made this using Google Earth &#8482;. The seismicity from the last 30 days (USGS feed) is plotted vs. depth (color, see legend on left).<br \/>\nThere is a legend that shows how moment tensors can be interpreted. Moment tensors are graphical solutions of seismic data that show two possible fault plane solutions. One must use local tectonics, along with other data, to be able to interpret which of the two possible solutions is correct. The legend shows how these two solutions are oriented for each example (Normal\/Extensional, Thrust\/Compressional, and Strike-Slip\/Shear). There is more about <a href=\"http:\/\/earthquake.usgs.gov\/learn\/glossary\/?term=moment%20tensor\" target=\"_blank\" rel=\"noopener\">moment tensors<\/a> and <a href=\"http:\/\/earthquake.usgs.gov\/learn\/topics\/beachball.php\" target=\"_blank\" rel=\"noopener\">focal mechanisms<\/a> at the USGS.<br \/>\nBased on the location of this earthquake (adjacent to the RFZ), I interpret this to be a right lateral (dextral) strike slip earthquake.<br \/>\nI plate some inset maps to help with the tectonic interpretation from <a href=\"http:\/\/www.sciencedirect.com\/science\/article\/pii\/S0377027309003163\" target=\"_blank\" rel=\"noopener\">Blatter and Hammersley (2010)<\/a> and <a href=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocs_boundary.pdf\" target=\"_blank\" rel=\"noopener\">Gaviria et al. (2013)<\/a>.<br \/>\n<a href=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/20160121_mexico_interpretation.pdf\" target=\"_blank\" rel=\"noopener\"><br \/>\n<img decoding=\"async\" src=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/20160121_mexico_interpretation.jpg\" width=\"100%\" alt=\"\" \/><\/a><br \/>\nFor more on the graphical representation of moment tensors and focal mechnisms, check this <a href=\"http:\/\/www.iris.edu\/hq\/programs\/education_and_outreach\/animations\/25\" target=\"_blank\" rel=\"noopener\">IRIS<\/a> video out:<br \/>\n<iframe loading=\"lazy\" width=\"420\" height=\"315\" src=\"https:\/\/www.youtube.com\/embed\/MomVOkyDdLo\" frameborder=\"0\" allowfullscreen><\/iframe><br \/>\nThis earthquake was not felt much in Mexico, based upon these USGS &#8220;Did You Feel It?&#8221; reports.<br \/>\n<a href=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/us10004g4l_ciim.pdf\" target=\"_blank\" rel=\"noopener\"><br \/>\n<img decoding=\"async\" src=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/us10004g4l_ciim.jpg\" width=\"100%\" alt=\"\" \/><\/a><br \/>\nGaviria et al. (2013) use magnetic anomalies to interpret the very complicated tectonics at the eastern part of the RFZ. Here is their plate tectonic map.<br \/>\n<a href=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_1.JPG\" target=\"_blank\" rel=\"noopener\"><br \/>\n<img decoding=\"async\" src=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_1.JPG\" width=\"100%\" alt=\"\" \/><\/a><br \/>\n<img decoding=\"async\" src=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_1_caption.JPG\" width=\"100%\" alt=\"\" \/><br \/>\nThis map includes focal mechanisms for earthquakes in the region. This helps them interpret the faulting.<br \/>\n<a href=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_8.JPG\" target=\"_blank\" rel=\"noopener\"><br \/>\n<img decoding=\"async\" src=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_8.JPG\" width=\"100%\" alt=\"\" \/><\/a><br \/>\n<img decoding=\"async\" src=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_8_caption.JPG\" width=\"100%\" alt=\"\" \/><br \/>\nHere is their figure showing the bathymetry of the region, along with their interpretation of where different fault systems are.<br \/>\n<a href=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_4.JPG\" target=\"_blank\" rel=\"noopener\"><br \/>\n<img decoding=\"async\" src=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_4.JPG\" width=\"100%\" alt=\"\" \/><\/a><br \/>\n<img decoding=\"async\" src=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_4_caption.JPG\" width=\"100%\" alt=\"\" \/><br \/>\nHere is the linework showing just the anomalies and faults.<br \/>\n<a href=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_6.JPG\" target=\"_blank\" rel=\"noopener\"><br \/>\n<img decoding=\"async\" src=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_6.JPG\" width=\"100%\" alt=\"\" \/><\/a><br \/>\n<img decoding=\"async\" src=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_6_caption.JPG\" alt=\"\" \/><br \/>\nThis map shows their interpretation for the development of the plate boundary from 3-1 Ma.<br \/>\n<a href=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_7.JPG\" target=\"_blank\" rel=\"noopener\"><br \/>\n<img decoding=\"async\" src=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_7.JPG\" width=\"100%\" alt=\"\" \/><\/a><br \/>\n<img decoding=\"async\" src=\"http:\/\/earthjay.com\/earthquakes\/20160121_mexico\/gaviria_etal_2013_magnetic_survey_rivera_cocos_boundary_fig_7_caption.JPG\" alt=\"\" \/><\/p>\n<ul>\nReferences:<\/p>\n<li>Blatter, D.L. and Hammersley, L., 2010. <a href=\"http:\/\/www.sciencedirect.com\/science\/article\/pii\/S0377027309003163\" target=\"_blank\" rel=\"noopener\">Impact of the Orozco Fracture Zone on the central Mexican Volcanic Belt<\/a> in Journal of Volcanology and Geothermal Research, v. 197, no. 1-4, p. 67-84.<\/li>\n<li>Gaviria, J.R.P.,  Guti\u00e9rre, C.A.M., Bandy, W.L., Michaud, F., 2013. <a href=\"http:\/\/www.elsevier.es\/en-revista-geofisica-internacional-80-articulo-morphology-and-magnetic-survey-of-90385573\" target=\"_blank\" rel=\"noopener\">Morphology and magnetic survey of the Rivera-Cocos plate boundary of Colima, Mexico<\/a> in Geofisica International, v. 52, no. 1., p. 73-85<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<div class=\"entry-summary\">\nWe just had an earthquake offshore of Colima, Mexico. This earthquake appears associated with the Rivera fracture zone (RFZ), a transform plate boundary separating the Rivera plate to the north and the Pacific plate to the south. The RFZ connects&hellip;\n<\/div>\n<div class=\"link-more\"><a href=\"https:\/\/earthjay.com\/?p=3576\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &ldquo;Earthquake Report: Rivera fracture zone, Mexico!&rdquo;<\/span>&hellip;<\/a><\/div>\n","protected":false},"author":3,"featured_media":3577,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0},"categories":[50,5,6,7,9,21,33,37],"tags":[],"aioseo_notices":[],"jetpack_featured_media_url":"https:\/\/earthjay.com\/wp-content\/uploads\/2016\/01\/20160121_mexico_interpretation_thumb-scaled.jpg","_links":{"self":[{"href":"https:\/\/earthjay.com\/index.php?rest_route=\/wp\/v2\/posts\/3576"}],"collection":[{"href":"https:\/\/earthjay.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/earthjay.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/earthjay.com\/index.php?rest_route=\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/earthjay.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3576"}],"version-history":[{"count":0,"href":"https:\/\/earthjay.com\/index.php?rest_route=\/wp\/v2\/posts\/3576\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/earthjay.com\/index.php?rest_route=\/wp\/v2\/media\/3577"}],"wp:attachment":[{"href":"https:\/\/earthjay.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3576"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/earthjay.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3576"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/earthjay.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3576"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}