{"id":1684,"date":"2023-12-07T21:45:28","date_gmt":"2023-12-07T21:45:28","guid":{"rendered":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/?post_type=chapter&p=1684"},"modified":"2023-12-11T15:50:47","modified_gmt":"2023-12-11T15:50:47","slug":"solution-exercise-11","status":"publish","type":"chapter","link":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/chapter\/solution-exercise-11\/","title":{"raw":"Solution Exercise 11\u200c\u200c","rendered":"Solution Exercise 11\u200c\u200c"},"content":{"raw":"

a) The drawing below shows two conjugate fracture sets typical of the extensional tectonic regime. The two fracture sets have the same strike, around N45E, and a similar dip value, around 75o<\/span><\/sup>, but one set dips toward NW and the other toward SE. This pattern is typical of the conjugate fractures generated in the Andersonian extensional tectonic regime (Figure 30<\/a>). They exhibit mutual abutting relationships (spots indicated by the black circles in the drawing below); the set that dips toward NW may abut against the set that dips toward SE, and vice versa. This means that these fractures were formed in the same tectonic event, which is consistent with the conjugate pattern.<\/p>\r\n\"\"\r\n\r\n \r\n

b) In the extensional regime, \u03c3<\/span><\/em><\/span>3<\/span><\/sub> is horizontal and perpendicular to the direction of the shear fractures (or normal faults). Therefore, its direction is N45W, \u03c3<\/span><\/em><\/span>1<\/span><\/sub> is vertical and \u03c3<\/span><\/em><\/span>2<\/span><\/sub> is parallel to the direction of the conjugate fractures. The typical dip of normal faults is around 60o<\/span><\/sup>. In this case, both sets dip at around 75o<\/span><\/sup>, meaning that 2\u03b8 <\/span><\/em>is approximately 30o<\/span><\/sup>. This indicates that they are hybrid fractures formed simultaneously through shear and opening modes.<\/p>\r\n

c) This fracture pattern provides connectivity. The fact that the fractures were formed by both shear and opening implies a larger fracture aperture than if they were formed only by shear. However, this applies to the time period when they were formed. In order to know whether the apertures are large at present would require systematic observations searching for evidence of groundwater flow (weathering, water leakage and vegetation) along these fractures and\/or conduction of hydraulic tests. The intersections of the two fracture sets are horizontal and increased horizontal channel flow along these intersections may be significant for groundwater flow in the aquifer.<\/p>\r\n

Click to return to where text linked to Exercise 11<\/strong><\/span><\/a><\/p>\r\n

Return to Exercise 11<\/strong><\/span><\/a><\/p>","rendered":"

a) The drawing below shows two conjugate fracture sets typical of the extensional tectonic regime. The two fracture sets have the same strike, around N45E, and a similar dip value, around 75o<\/span><\/sup>, but one set dips toward NW and the other toward SE. This pattern is typical of the conjugate fractures generated in the Andersonian extensional tectonic regime (Figure 30<\/a>). They exhibit mutual abutting relationships (spots indicated by the black circles in the drawing below); the set that dips toward NW may abut against the set that dips toward SE, and vice versa. This means that these fractures were formed in the same tectonic event, which is consistent with the conjugate pattern.<\/p>\n

\"\"<\/p>\n

 <\/p>\n

b) In the extensional regime, \u03c3<\/span><\/em><\/span>3<\/span><\/sub> is horizontal and perpendicular to the direction of the shear fractures (or normal faults). Therefore, its direction is N45W, \u03c3<\/span><\/em><\/span>1<\/span><\/sub> is vertical and \u03c3<\/span><\/em><\/span>2<\/span><\/sub> is parallel to the direction of the conjugate fractures. The typical dip of normal faults is around 60o<\/span><\/sup>. In this case, both sets dip at around 75o<\/span><\/sup>, meaning that 2\u03b8 <\/span><\/em>is approximately 30o<\/span><\/sup>. This indicates that they are hybrid fractures formed simultaneously through shear and opening modes.<\/p>\n

c) This fracture pattern provides connectivity. The fact that the fractures were formed by both shear and opening implies a larger fracture aperture than if they were formed only by shear. However, this applies to the time period when they were formed. In order to know whether the apertures are large at present would require systematic observations searching for evidence of groundwater flow (weathering, water leakage and vegetation) along these fractures and\/or conduction of hydraulic tests. The intersections of the two fracture sets are horizontal and increased horizontal channel flow along these intersections may be significant for groundwater flow in the aquifer.<\/p>\n

Click to return to where text linked to Exercise 11<\/strong><\/span><\/a><\/p>\n

Return to Exercise 11<\/strong><\/span><\/a><\/p>\n","protected":false},"author":6,"menu_order":11,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-1684","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\/1684","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\/1684\/revisions"}],"predecessor-version":[{"id":2119,"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/pressbooks\/v2\/chapters\/1684\/revisions\/2119"}],"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\/1684\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/wp\/v2\/media?parent=1684"}],"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=1684"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/wp\/v2\/contributor?post=1684"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/books.gw-project.org\/structural-geology-applied-to-fractured-aquifer-characterization\/wp-json\/wp\/v2\/license?post=1684"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}