Thermal segmentation of mid‐ocean ridge‐transform faults
3‐D finite element simulations are used to calculate thermal structures and mantle flow fields underlying mid‐ocean ridge‐transform faults (RTFs) composed of two fault segments separated by an orthogonal step over. Using fault lengths and slip rates, we derive an empirical scaling relation for the c...
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| creator | Wolfson‐Schwehr, Monica Boettcher, Margaret S. Behn, Mark D. |
| description | 3‐D finite element simulations are used to calculate thermal structures and mantle flow fields underlying mid‐ocean ridge‐transform faults (RTFs) composed of two fault segments separated by an orthogonal step over. Using fault lengths and slip rates, we derive an empirical scaling relation for the critical step over length (
LS˜), which marks the transition from predominantly horizontal to predominantly vertical mantle flow at the base of the lithosphere under a step over. Using the ratio of step over length (LS) to
LS˜, we define three degrees of segmentation: first‐degree, corresponding to type I step overs (
LS/LS˜ ≥ 3); second‐degree, corresponding to type II step overs (1 ≤
LS/LS˜ |
| doi_str_mv | 10.1002/2017GC006967 |
| format | Article |
| fullrecord | <record><control><sourceid>proquest_24P</sourceid><recordid>TN_cdi_proquest_journals_1951053718</recordid><sourceformat>XML</sourceformat><sourcesystem>PC</sourcesystem><sourcerecordid>1951053718</sourcerecordid><originalsourceid>FETCH-LOGICAL-a3683-4024a2a1b2c7cd6e09677f1ba8b0168d7f04bb9c525f854004f26f864adac5173</originalsourceid><addsrcrecordid>eNp9kM1Kw0AUhQdRsFZ3PkDArdF757_gRkqNguCmrodJMlNTkkydSZHufASf0ScxUhddubrnwsc5h0PIJcINAtBbCqiKOYCcSXVEJiioyClQdXygT8lZSmsA5ELoCblbvrnY2TZLbtW5frBDE_os-Kxr6u_Pr1A522exqVdu_IZo--RD7DJvt-2QzsmJt21yF393Sl4fFsv5Y_78UjzN759zy6RmOQfKLbVY0kpVtXQw1lMeS6tLQKlr5YGX5awaK3otOAD3VHotua1tJVCxKbna-25ieN-6NJh12MZ-jDQ4EwiCKdQjdb2nqhhSis6bTWw6G3cGwfzuYw73GXG2xz-a1u3-ZU1RFAuKTDP2A1v2Zx8</addsrcrecordid><sourcetype>Aggregation Database</sourcetype><iscdi>true</iscdi><recordtype>article</recordtype><pqid>1951053718</pqid></control><display><type>article</type><title>Thermal segmentation of mid‐ocean ridge‐transform faults</title><source>Wiley Online Library Open Access</source><creator>Wolfson‐Schwehr, Monica ; Boettcher, Margaret S. ; Behn, Mark D.</creator><creatorcontrib>Wolfson‐Schwehr, Monica ; Boettcher, Margaret S. ; Behn, Mark D.</creatorcontrib><description>3‐D finite element simulations are used to calculate thermal structures and mantle flow fields underlying mid‐ocean ridge‐transform faults (RTFs) composed of two fault segments separated by an orthogonal step over. Using fault lengths and slip rates, we derive an empirical scaling relation for the critical step over length (
LS˜), which marks the transition from predominantly horizontal to predominantly vertical mantle flow at the base of the lithosphere under a step over. Using the ratio of step over length (LS) to
LS˜, we define three degrees of segmentation: first‐degree, corresponding to type I step overs (
LS/LS˜ ≥ 3); second‐degree, corresponding to type II step overs (1 ≤
LS/LS˜ < 3); and third‐degree, corresponding to type III step overs (
LS/LS˜ <1). In first‐degree segmentation, thermal structures and mantle upwelling patterns under a step over are similar to those of mature ridges, where normal mid‐ocean ridge basalts (MORBs) form. The seismogenic area under first‐degree segmentation is characteristic of two, isolated faults. Second‐degree segmentation creates pull‐apart basins with subdued melt generation, and intratransform spreading centers with enriched MORBs. The seismogenic area of RTFs under second‐degree segmentation is greater than that of two isolated faults, but less than that of an unsegmented RTF. Under third‐degree segmentation, mantle flow is predominantly horizontal, resulting in little lithospheric thinning and little to no melt generation. The total seismogenic area under third‐degree segmentation approaches that of an unsegmented RTF. Our scaling relations characterize the degree of segmentation due to step overs along transform faults and provide insight into RTF frictional processes, seismogenic behavior, and melt transport.
Plain Language Summary
Mid‐ocean ridge‐transform faults (i.e., strike‐slip faults that accommodate lateral motion associated with seafloor spreading) are typically viewed as geometrically simple structures, where a continuous fault is located between two spreading ridges. However, high‐resolution seafloor mapping has shown that the structure of these fault systems is often quite complex. Mid‐ocean ridge‐transform faults may be composed of two or more individual fault strands separated by a step over. Using results of numerical simulations, we show that the form of the step over is expected to vary systematically from small extensional basins to active spreading ridge segments, depending on the length of the step over, the length of the adjacent fault segments, and the plate tectonic spreading rate. Additionally, our results suggest that the chemistry of mid‐ocean ridge basalts produced at the step over is expected to change systematically with the step over length. This work shows that while the structure of transform faults can significantly affect the thermal structure of the region, it can readily be determined from regional plate tectonic parameters (fault lengths, step over length, and spreading rate). Furthermore, this work provides key insights into frictional processes, seismic behavior, and melt transport along oceanic transform plate boundary faults.
Key Points
The type of step overs between ridge‐transform fault segments is determined from the plate spreading rate and fault segment lengths
A scaling relation for the critical step over length at which mantle flow starts to thin the lithosphere is derived
Na_8.0 concentrations in dredged basalts follow the predicted trend based on the critical step over length</description><identifier>ISSN: 1525-2027</identifier><identifier>EISSN: 1525-2027</identifier><identifier>DOI: 10.1002/2017GC006967</identifier><language>eng</language><publisher>Washington: John Wiley & Sons, Inc</publisher><subject>Area ; Basalt ; Basins ; Fault lines ; fault segmentation ; fault thermal structure ; Faults ; intratransform spreading center ; Lava ; Length ; Lithosphere ; Mantle ; melt transport ; Mid-ocean ridges ; Numerical simulations ; Ocean circulation ; Ocean floor ; oceanic transform fault ; Oceans ; Plate boundaries ; Plate tectonics ; Ridges ; Scaling ; Seafloor mapping ; Seafloor spreading ; Seismic activity ; Spreading centres ; Strike-slip faults ; Structures ; Thermal structure ; Transform faults ; Transform plate boundaries ; Transport ; Upwelling</subject><ispartof>Geochemistry, geophysics, geosystems : G3, 2017-09, Vol.18 (9), p.3405-3418</ispartof><rights>2017. American Geophysical Union. All Rights Reserved.</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-a3683-4024a2a1b2c7cd6e09677f1ba8b0168d7f04bb9c525f854004f26f864adac5173</citedby><cites>FETCH-LOGICAL-a3683-4024a2a1b2c7cd6e09677f1ba8b0168d7f04bb9c525f854004f26f864adac5173</cites><orcidid>0000-0002-2001-1335 ; 0000-0002-5031-7116 ; 0000-0001-5885-8606</orcidid></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktopdf>$$Uhttps://onlinelibrary.wiley.com/doi/pdf/10.1002%2F2017GC006967$$EPDF$$P50$$Gwiley$$H</linktopdf><linktohtml>$$Uhttps://onlinelibrary.wiley.com/doi/full/10.1002%2F2017GC006967$$EHTML$$P50$$Gwiley$$H</linktohtml><link.rule.ids>314,776,780,1411,11541,27901,27902,45550,45551,46027,46451</link.rule.ids><linktorsrc>$$Uhttps://onlinelibrary.wiley.com/doi/abs/10.1002%2F2017GC006967$$EView_record_in_Wiley-Blackwell$$FView_record_in_$$GWiley-Blackwell</linktorsrc></links><search><creatorcontrib>Wolfson‐Schwehr, Monica</creatorcontrib><creatorcontrib>Boettcher, Margaret S.</creatorcontrib><creatorcontrib>Behn, Mark D.</creatorcontrib><title>Thermal segmentation of mid‐ocean ridge‐transform faults</title><title>Geochemistry, geophysics, geosystems : G3</title><description>3‐D finite element simulations are used to calculate thermal structures and mantle flow fields underlying mid‐ocean ridge‐transform faults (RTFs) composed of two fault segments separated by an orthogonal step over. Using fault lengths and slip rates, we derive an empirical scaling relation for the critical step over length (
LS˜), which marks the transition from predominantly horizontal to predominantly vertical mantle flow at the base of the lithosphere under a step over. Using the ratio of step over length (LS) to
LS˜, we define three degrees of segmentation: first‐degree, corresponding to type I step overs (
LS/LS˜ ≥ 3); second‐degree, corresponding to type II step overs (1 ≤
LS/LS˜ < 3); and third‐degree, corresponding to type III step overs (
LS/LS˜ <1). In first‐degree segmentation, thermal structures and mantle upwelling patterns under a step over are similar to those of mature ridges, where normal mid‐ocean ridge basalts (MORBs) form. The seismogenic area under first‐degree segmentation is characteristic of two, isolated faults. Second‐degree segmentation creates pull‐apart basins with subdued melt generation, and intratransform spreading centers with enriched MORBs. The seismogenic area of RTFs under second‐degree segmentation is greater than that of two isolated faults, but less than that of an unsegmented RTF. Under third‐degree segmentation, mantle flow is predominantly horizontal, resulting in little lithospheric thinning and little to no melt generation. The total seismogenic area under third‐degree segmentation approaches that of an unsegmented RTF. Our scaling relations characterize the degree of segmentation due to step overs along transform faults and provide insight into RTF frictional processes, seismogenic behavior, and melt transport.
Plain Language Summary
Mid‐ocean ridge‐transform faults (i.e., strike‐slip faults that accommodate lateral motion associated with seafloor spreading) are typically viewed as geometrically simple structures, where a continuous fault is located between two spreading ridges. However, high‐resolution seafloor mapping has shown that the structure of these fault systems is often quite complex. Mid‐ocean ridge‐transform faults may be composed of two or more individual fault strands separated by a step over. Using results of numerical simulations, we show that the form of the step over is expected to vary systematically from small extensional basins to active spreading ridge segments, depending on the length of the step over, the length of the adjacent fault segments, and the plate tectonic spreading rate. Additionally, our results suggest that the chemistry of mid‐ocean ridge basalts produced at the step over is expected to change systematically with the step over length. This work shows that while the structure of transform faults can significantly affect the thermal structure of the region, it can readily be determined from regional plate tectonic parameters (fault lengths, step over length, and spreading rate). Furthermore, this work provides key insights into frictional processes, seismic behavior, and melt transport along oceanic transform plate boundary faults.
Key Points
The type of step overs between ridge‐transform fault segments is determined from the plate spreading rate and fault segment lengths
A scaling relation for the critical step over length at which mantle flow starts to thin the lithosphere is derived
Na_8.0 concentrations in dredged basalts follow the predicted trend based on the critical step over length</description><subject>Area</subject><subject>Basalt</subject><subject>Basins</subject><subject>Fault lines</subject><subject>fault segmentation</subject><subject>fault thermal structure</subject><subject>Faults</subject><subject>intratransform spreading center</subject><subject>Lava</subject><subject>Length</subject><subject>Lithosphere</subject><subject>Mantle</subject><subject>melt transport</subject><subject>Mid-ocean ridges</subject><subject>Numerical simulations</subject><subject>Ocean circulation</subject><subject>Ocean floor</subject><subject>oceanic transform fault</subject><subject>Oceans</subject><subject>Plate boundaries</subject><subject>Plate tectonics</subject><subject>Ridges</subject><subject>Scaling</subject><subject>Seafloor mapping</subject><subject>Seafloor spreading</subject><subject>Seismic activity</subject><subject>Spreading centres</subject><subject>Strike-slip faults</subject><subject>Structures</subject><subject>Thermal structure</subject><subject>Transform faults</subject><subject>Transform plate boundaries</subject><subject>Transport</subject><subject>Upwelling</subject><issn>1525-2027</issn><issn>1525-2027</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2017</creationdate><recordtype>article</recordtype><recordid>eNp9kM1Kw0AUhQdRsFZ3PkDArdF757_gRkqNguCmrodJMlNTkkydSZHufASf0ScxUhddubrnwsc5h0PIJcINAtBbCqiKOYCcSXVEJiioyClQdXygT8lZSmsA5ELoCblbvrnY2TZLbtW5frBDE_os-Kxr6u_Pr1A522exqVdu_IZo--RD7DJvt-2QzsmJt21yF393Sl4fFsv5Y_78UjzN759zy6RmOQfKLbVY0kpVtXQw1lMeS6tLQKlr5YGX5awaK3otOAD3VHotua1tJVCxKbna-25ieN-6NJh12MZ-jDQ4EwiCKdQjdb2nqhhSis6bTWw6G3cGwfzuYw73GXG2xz-a1u3-ZU1RFAuKTDP2A1v2Zx8</recordid><startdate>201709</startdate><enddate>201709</enddate><creator>Wolfson‐Schwehr, Monica</creator><creator>Boettcher, Margaret S.</creator><creator>Behn, Mark D.</creator><general>John Wiley & Sons, Inc</general><scope>AAYXX</scope><scope>CITATION</scope><scope>7TG</scope><scope>7TN</scope><scope>F1W</scope><scope>H96</scope><scope>KL.</scope><scope>L.G</scope><orcidid>https://orcid.org/0000-0002-2001-1335</orcidid><orcidid>https://orcid.org/0000-0002-5031-7116</orcidid><orcidid>https://orcid.org/0000-0001-5885-8606</orcidid></search><sort><creationdate>201709</creationdate><title>Thermal segmentation of mid‐ocean ridge‐transform faults</title><author>Wolfson‐Schwehr, Monica ; Boettcher, Margaret S. ; Behn, Mark D.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-a3683-4024a2a1b2c7cd6e09677f1ba8b0168d7f04bb9c525f854004f26f864adac5173</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2017</creationdate><topic>Area</topic><topic>Basalt</topic><topic>Basins</topic><topic>Fault lines</topic><topic>fault segmentation</topic><topic>fault thermal structure</topic><topic>Faults</topic><topic>intratransform spreading center</topic><topic>Lava</topic><topic>Length</topic><topic>Lithosphere</topic><topic>Mantle</topic><topic>melt transport</topic><topic>Mid-ocean ridges</topic><topic>Numerical simulations</topic><topic>Ocean circulation</topic><topic>Ocean floor</topic><topic>oceanic transform fault</topic><topic>Oceans</topic><topic>Plate boundaries</topic><topic>Plate tectonics</topic><topic>Ridges</topic><topic>Scaling</topic><topic>Seafloor mapping</topic><topic>Seafloor spreading</topic><topic>Seismic activity</topic><topic>Spreading centres</topic><topic>Strike-slip faults</topic><topic>Structures</topic><topic>Thermal structure</topic><topic>Transform faults</topic><topic>Transform plate boundaries</topic><topic>Transport</topic><topic>Upwelling</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Wolfson‐Schwehr, Monica</creatorcontrib><creatorcontrib>Boettcher, Margaret S.</creatorcontrib><creatorcontrib>Behn, Mark D.</creatorcontrib><collection>CrossRef</collection><collection>Meteorological & Geoastrophysical Abstracts</collection><collection>Oceanic Abstracts</collection><collection>ASFA: Aquatic Sciences and Fisheries Abstracts</collection><collection>Aquatic Science & Fisheries Abstracts (ASFA) 2: Ocean Technology, Policy & Non-Living Resources</collection><collection>Meteorological & Geoastrophysical Abstracts - Academic</collection><collection>Aquatic Science & Fisheries Abstracts (ASFA) Professional</collection><jtitle>Geochemistry, geophysics, geosystems : G3</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext_linktorsrc</fulltext></delivery><addata><au>Wolfson‐Schwehr, Monica</au><au>Boettcher, Margaret S.</au><au>Behn, Mark D.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Thermal segmentation of mid‐ocean ridge‐transform faults</atitle><jtitle>Geochemistry, geophysics, geosystems : G3</jtitle><date>2017-09</date><risdate>2017</risdate><volume>18</volume><issue>9</issue><spage>3405</spage><epage>3418</epage><pages>3405-3418</pages><issn>1525-2027</issn><eissn>1525-2027</eissn><abstract>3‐D finite element simulations are used to calculate thermal structures and mantle flow fields underlying mid‐ocean ridge‐transform faults (RTFs) composed of two fault segments separated by an orthogonal step over. Using fault lengths and slip rates, we derive an empirical scaling relation for the critical step over length (
LS˜), which marks the transition from predominantly horizontal to predominantly vertical mantle flow at the base of the lithosphere under a step over. Using the ratio of step over length (LS) to
LS˜, we define three degrees of segmentation: first‐degree, corresponding to type I step overs (
LS/LS˜ ≥ 3); second‐degree, corresponding to type II step overs (1 ≤
LS/LS˜ < 3); and third‐degree, corresponding to type III step overs (
LS/LS˜ <1). In first‐degree segmentation, thermal structures and mantle upwelling patterns under a step over are similar to those of mature ridges, where normal mid‐ocean ridge basalts (MORBs) form. The seismogenic area under first‐degree segmentation is characteristic of two, isolated faults. Second‐degree segmentation creates pull‐apart basins with subdued melt generation, and intratransform spreading centers with enriched MORBs. The seismogenic area of RTFs under second‐degree segmentation is greater than that of two isolated faults, but less than that of an unsegmented RTF. Under third‐degree segmentation, mantle flow is predominantly horizontal, resulting in little lithospheric thinning and little to no melt generation. The total seismogenic area under third‐degree segmentation approaches that of an unsegmented RTF. Our scaling relations characterize the degree of segmentation due to step overs along transform faults and provide insight into RTF frictional processes, seismogenic behavior, and melt transport.
Plain Language Summary
Mid‐ocean ridge‐transform faults (i.e., strike‐slip faults that accommodate lateral motion associated with seafloor spreading) are typically viewed as geometrically simple structures, where a continuous fault is located between two spreading ridges. However, high‐resolution seafloor mapping has shown that the structure of these fault systems is often quite complex. Mid‐ocean ridge‐transform faults may be composed of two or more individual fault strands separated by a step over. Using results of numerical simulations, we show that the form of the step over is expected to vary systematically from small extensional basins to active spreading ridge segments, depending on the length of the step over, the length of the adjacent fault segments, and the plate tectonic spreading rate. Additionally, our results suggest that the chemistry of mid‐ocean ridge basalts produced at the step over is expected to change systematically with the step over length. This work shows that while the structure of transform faults can significantly affect the thermal structure of the region, it can readily be determined from regional plate tectonic parameters (fault lengths, step over length, and spreading rate). Furthermore, this work provides key insights into frictional processes, seismic behavior, and melt transport along oceanic transform plate boundary faults.
Key Points
The type of step overs between ridge‐transform fault segments is determined from the plate spreading rate and fault segment lengths
A scaling relation for the critical step over length at which mantle flow starts to thin the lithosphere is derived
Na_8.0 concentrations in dredged basalts follow the predicted trend based on the critical step over length</abstract><cop>Washington</cop><pub>John Wiley & Sons, Inc</pub><doi>10.1002/2017GC006967</doi><tpages>14</tpages><orcidid>https://orcid.org/0000-0002-2001-1335</orcidid><orcidid>https://orcid.org/0000-0002-5031-7116</orcidid><orcidid>https://orcid.org/0000-0001-5885-8606</orcidid><oa>free_for_read</oa></addata></record> |
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| ispartof | Geochemistry, geophysics, geosystems : G3, 2017-09, Vol.18 (9), p.3405-3418 |
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| subjects | Area Basalt Basins Fault lines fault segmentation fault thermal structure Faults intratransform spreading center Lava Length Lithosphere Mantle melt transport Mid-ocean ridges Numerical simulations Ocean circulation Ocean floor oceanic transform fault Oceans Plate boundaries Plate tectonics Ridges Scaling Seafloor mapping Seafloor spreading Seismic activity Spreading centres Strike-slip faults Structures Thermal structure Transform faults Transform plate boundaries Transport Upwelling |
| title | Thermal segmentation of mid‐ocean ridge‐transform faults |
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