{"id":1679,"date":"2023-12-07T21:40:59","date_gmt":"2023-12-07T21:40:59","guid":{"rendered":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/?post_type=chapter&#038;p=1679"},"modified":"2023-12-11T15:21:15","modified_gmt":"2023-12-11T15:21:15","slug":"solution-exercise-9","status":"publish","type":"chapter","link":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/chapter\/solution-exercise-9\/","title":{"raw":"Solution Exercise 9\u200c\u200c","rendered":"Solution Exercise 9\u200c\u200c"},"content":{"raw":"<p class=\"hanging-indent\">a) The image below (modified from Dunne &amp; Hancock, 1994) shows the orientation of the principal stresses with regard to a joint that bears a plume with a horizontal axis. The N30W\/90 fracture bears a plume on its surface, which indicates that it propagated through the opening mode; thus, it is a joint. Because joints are perpendicular to <span class=\"s23\"><em><span class=\"s23\">\u03c3<\/span><\/em><\/span><sub><span class=\"s31\">3<\/span><\/sub>, this stress is horizontal and strikes N60E. The axis of the plume is horizontal and, given that <span class=\"s23\"><em><span class=\"s23\">\u03c3<\/span><\/em><\/span><sub><span class=\"s31\">1<\/span><\/sub> is parallel to it (as shown in the image below), this stress is horizontal and strikes N30W. Because both <span class=\"s23\"><em><span class=\"s23\">\u03c3<\/span><\/em><\/span><sub><span class=\"s31\">3<\/span><\/sub> and <span class=\"s23\"><em><span class=\"s23\">\u03c3<\/span><\/em><\/span><sub><span class=\"s31\">1<\/span><\/sub> are horizontal, these fractures were formed under a strike-slip regime.<\/p>\r\n&nbsp;\r\n\r\n<img class=\" wp-image-1318 aligncenter\" src=\"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-content\/uploads\/sites\/35\/2023\/12\/Image_150.jpg\" alt=\"\" width=\"463\" height=\"389\" \/>\r\n\r\n&nbsp;\r\n<p class=\"hanging-indent\">b) The EW\/42SW fracture has a dip that is closer to the one of the thrust faults. However, the typical dip of these faults is 30<span class=\"s24\">o<\/span> or less. So, more data, such as surface features (plume or striae, for example) and\/or fracture pattern (conjugate or parallel) are needed in order to know the propagation mode, the principal stresses and the tectonic regime that produced this fracture.<\/p>\r\n<p class=\"hanging-indent\">c) It is not possible that both fracture sets have been formed during the same tectonic event, as the N30W\/90 fracture was formed in the strike-slip regime and fractures of intermediate dip do not fit into any type of fracture pattern that is generated by that regime (<span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/chapter\/1191\/#fig-30\">Figure 30<\/a><\/span>).<\/p>\r\n<p style=\"text-align: right;\"><span style=\"text-decoration: underline;\"><strong><a href=\"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/chapter\/3-7-highlights-on-tectonic-regimes-and-groundwater-flow-with-opportunities-to-exercise-knowledge-gained-by-reading-sections-1-2-and-3\/#exercise-8\">Click to return to where text linked to Exercise 9<\/a>\r\n<\/strong><\/span><\/p>\r\n<p style=\"text-align: right;\"><span style=\"text-decoration: underline;\"><strong><a href=\"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/chapter\/exercise-9\/\">Click to return to Exercise 9<\/a>\r\n<\/strong><\/span><\/p>","rendered":"<p class=\"hanging-indent\">a) The image below (modified from Dunne &amp; Hancock, 1994) shows the orientation of the principal stresses with regard to a joint that bears a plume with a horizontal axis. The N30W\/90 fracture bears a plume on its surface, which indicates that it propagated through the opening mode; thus, it is a joint. Because joints are perpendicular to <span class=\"s23\"><em><span class=\"s23\">\u03c3<\/span><\/em><\/span><sub><span class=\"s31\">3<\/span><\/sub>, this stress is horizontal and strikes N60E. The axis of the plume is horizontal and, given that <span class=\"s23\"><em><span class=\"s23\">\u03c3<\/span><\/em><\/span><sub><span class=\"s31\">1<\/span><\/sub> is parallel to it (as shown in the image below), this stress is horizontal and strikes N30W. Because both <span class=\"s23\"><em><span class=\"s23\">\u03c3<\/span><\/em><\/span><sub><span class=\"s31\">3<\/span><\/sub> and <span class=\"s23\"><em><span class=\"s23\">\u03c3<\/span><\/em><\/span><sub><span class=\"s31\">1<\/span><\/sub> are horizontal, these fractures were formed under a strike-slip regime.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1318 aligncenter\" src=\"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-content\/uploads\/sites\/35\/2023\/12\/Image_150.jpg\" alt=\"\" width=\"463\" height=\"389\" srcset=\"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-content\/uploads\/sites\/35\/2023\/12\/Image_150.jpg 264w, https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-content\/uploads\/sites\/35\/2023\/12\/Image_150-65x55.jpg 65w, https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-content\/uploads\/sites\/35\/2023\/12\/Image_150-225x189.jpg 225w\" sizes=\"auto, (max-width: 463px) 100vw, 463px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p class=\"hanging-indent\">b) The EW\/42SW fracture has a dip that is closer to the one of the thrust faults. However, the typical dip of these faults is 30<span class=\"s24\">o<\/span> or less. So, more data, such as surface features (plume or striae, for example) and\/or fracture pattern (conjugate or parallel) are needed in order to know the propagation mode, the principal stresses and the tectonic regime that produced this fracture.<\/p>\n<p class=\"hanging-indent\">c) It is not possible that both fracture sets have been formed during the same tectonic event, as the N30W\/90 fracture was formed in the strike-slip regime and fractures of intermediate dip do not fit into any type of fracture pattern that is generated by that regime (<span style=\"color: #000000;\"><a style=\"color: #000000;\" href=\"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/chapter\/1191\/#fig-30\">Figure 30<\/a><\/span>).<\/p>\n<p style=\"text-align: right;\"><span style=\"text-decoration: underline;\"><strong><a href=\"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/chapter\/3-7-highlights-on-tectonic-regimes-and-groundwater-flow-with-opportunities-to-exercise-knowledge-gained-by-reading-sections-1-2-and-3\/#exercise-8\">Click to return to where text linked to Exercise 9<\/a><br \/>\n<\/strong><\/span><\/p>\n<p style=\"text-align: right;\"><span style=\"text-decoration: underline;\"><strong><a href=\"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/chapter\/exercise-9\/\">Click to return to Exercise 9<\/a><br \/>\n<\/strong><\/span><\/p>\n","protected":false},"author":6,"menu_order":9,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-1679","chapter","type-chapter","status-publish","hentry"],"part":1650,"_links":{"self":[{"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/pressbooks\/v2\/chapters\/1679","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/wp\/v2\/users\/6"}],"version-history":[{"count":8,"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/pressbooks\/v2\/chapters\/1679\/revisions"}],"predecessor-version":[{"id":2099,"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/pressbooks\/v2\/chapters\/1679\/revisions\/2099"}],"part":[{"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/pressbooks\/v2\/parts\/1650"}],"metadata":[{"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/pressbooks\/v2\/chapters\/1679\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/wp\/v2\/media?parent=1679"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/pressbooks\/v2\/chapter-type?post=1679"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/wp\/v2\/contributor?post=1679"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/wp\/v2\/license?post=1679"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}