Metamorphic dehydration reactions and fluid movement in accretionary prisms have been linked to the recently discovered episodic tremor and slip (ETS) earthquake events along subduction zones, but prior studies lack the detail to effectively test the hypothesis that fluid flow triggers ETS events. I conducted field work along a 52.5 km transect on the Olympic Peninsula metasedimentary accretionary prism of the Cascadia subduction zone, and collected approximately 40 representative samples of sandstone and mudrock that were buried to 6–15 km. This depth range intersects the 10–50 km depth range of ETS events. My objectives are to quantify the water flow recorded in rocks of the Olympic Peninsula via petrographic, whole rock, and isotopic analyses to test the prediction that water release increases at ~10 km depth, creating fluid overpressure needed to trigger seismicity.
I calculated that on the Olympic Peninsula 1 km3 of 50% sandstone and 50% mudrock loses ~105 kg H2O/yr during burial from 6–14 km depth, comparable to the values expected from large-scale fluid budget models. Quartz veins that compose 0.5–1% of the Obstruction Peak site (~14 km burial depth) are important records of fluid flow quantity and origin. δ18O values of +11.8‰ to +15.2‰ indicate that vein H2O originated from metamorphic reactions. Flow recorded by 1 km3 of rock containing 0.5–1% quartz veins is >106 kg H2O/yr, comparable to the values 2 × 107 to 2 × 108 kg H2O/yr modeled at compositionally similar subduction zones to produce fluid overpressure conditions. I observed fibrous quartz veins, which also indicate fluid overpressure conditions were reached and support my H2O flow estimates. Therefore, Olympic Peninsula rocks at depths of ~10–14 km record dehydration and fluid overpressure large enough to trigger subduction zone seismicity.
","abstract_html":"<p>Metamorphic dehydration reactions and fluid movement in accretionary prisms have been linked to the recently discovered episodic tremor and slip (ETS) earthquake events along subduction zones, but prior studies lack the detail to effectively test the hypothesis that fluid flow triggers ETS events. I conducted field work along a 52.5 km transect on the Olympic Peninsula metasedimentary accretionary prism of the Cascadia subduction zone, and collected approximately 40 representative samples of sandstone and mudrock that were buried to 6–15 km. This depth range intersects the 10–50 km depth range of ETS events. My objectives are to quantify the water flow recorded in rocks of the Olympic Peninsula via petrographic, whole rock, and isotopic analyses to test the prediction that water release increases at ~10 km depth, creating fluid overpressure needed to trigger seismicity.</p> <p>I calculated that on the Olympic Peninsula 1 km<sup>3</sup> of 50% sandstone and 50% mudrock loses ~10<sup>5</sup> kg H<sub>2</sub>O/yr during burial from 6–14 km depth, comparable to the values expected from large-scale fluid budget models. Quartz veins that compose 0.5–1% of the Obstruction Peak site (~14 km burial depth) are important records of fluid flow quantity and origin. δ<sup>18</sup>O values of +11.8‰ to +15.2‰ indicate that vein H<sub>2</sub>O originated from metamorphic reactions. Flow recorded by 1 km<sup>3</sup> of rock containing 0.5–1% quartz veins is >10<sup>6</sup> kg H<sub>2</sub>O/yr, comparable to the values 2 × 10<sup>7</sup> to 2 × 10<sup>8</sup> kg H<sub>2</sub>O/yr modeled at compositionally similar subduction zones to produce fluid overpressure conditions. I observed fibrous quartz veins, which also indicate fluid overpressure conditions were reached and support my H<sub>2</sub>O flow estimates. Therefore, Olympic Peninsula rocks at depths of ~10–14 km record dehydration and fluid overpressure large enough to trigger subduction zone seismicity.</p>","abstract_has_math":false,"creators":["Rotman, Holly Makena MacFadden"],"institution":null,"degree_name":"Master of Science (MS)","degree_level":null,"degree_discipline":"Geological Sciences","degree_department":null,"school":null,"contributors":["Chris Mattinson","Careyt Gazis","Tim Melbourne"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2010,"date_issued":"2010-01-01T08:00:00Z","date_published":"2010-01-01T08:00:00Z","updated_at":"2026-07-24T01:37:54Z","subjects":["sedimentary rocks","seismicity","Olympic Penninsula","Washington State","Dehydration reactions","Geophysics and Seismology","Hydrology","Mineral Physics"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://digitalcommons.cwu.edu/etd/1460","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Chris Mattinson","Careyt Gazis","Tim Melbourne"]},{"key":"dc:creator","label":"Author","values":["Rotman, Holly Makena MacFadden"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2020-12-22T08:00:00Z"]},{"key":"dc:type","label":"Dc Type","values":["Text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Geological Sciences"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science (MS)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["sedimentary rocks","seismicity","Olympic Penninsula","Washington State","Dehydration reactions","Geophysics and Seismology","Hydrology","Mineral Physics"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://digitalcommons.cwu.edu/etd/1460"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Metamorphic dehydration reactions and fluid movement in accretionary prisms have been linked to the recently discovered episodic tremor and slip (ETS) earthquake events along subduction zones, but prior studies lack the detail to effectively test the hypothesis that fluid flow triggers ETS events. I conducted field work along a 52.5 km transect on the Olympic Peninsula metasedimentary accretionary prism of the Cascadia subduction zone, and collected approximately 40 representative samples of sandstone and mudrock that were buried to 6–15 km. This depth range intersects the 10–50 km depth range of ETS events. My objectives are to quantify the water flow recorded in rocks of the Olympic Peninsula via petrographic, whole rock, and isotopic analyses to test the prediction that water release increases at ~10 km depth, creating fluid overpressure needed to trigger seismicity.
I calculated that on the Olympic Peninsula 1 km3 of 50% sandstone and 50% mudrock loses ~105 kg H2O/yr during burial from 6–14 km depth, comparable to the values expected from large-scale fluid budget models. Quartz veins that compose 0.5–1% of the Obstruction Peak site (~14 km burial depth) are important records of fluid flow quantity and origin. δ18O values of +11.8‰ to +15.2‰ indicate that vein H2O originated from metamorphic reactions. Flow recorded by 1 km3 of rock containing 0.5–1% quartz veins is >106 kg H2O/yr, comparable to the values 2 × 107 to 2 × 108 kg H2O/yr modeled at compositionally similar subduction zones to produce fluid overpressure conditions. I observed fibrous quartz veins, which also indicate fluid overpressure conditions were reached and support my H2O flow estimates. Therefore, Olympic Peninsula rocks at depths of ~10–14 km record dehydration and fluid overpressure large enough to trigger subduction zone seismicity.
"]},{"key":"dc:title","label":"Title","values":["Fluid Budget of Metasedimentary Rocks from a Tertiary Accretionary Prism and Connections to Seismicity, Olympic Peninsula, Northwest Washington State"]}]}],"canonical_facts":{"dc:contributor":["Chris Mattinson","Careyt Gazis","Tim Melbourne"],"dc:creator":["Rotman, Holly Makena MacFadden"],"dc:date.available":["2020-12-22T08:00:00Z"],"dc:description.abstract":["Metamorphic dehydration reactions and fluid movement in accretionary prisms have been linked to the recently discovered episodic tremor and slip (ETS) earthquake events along subduction zones, but prior studies lack the detail to effectively test the hypothesis that fluid flow triggers ETS events. I conducted field work along a 52.5 km transect on the Olympic Peninsula metasedimentary accretionary prism of the Cascadia subduction zone, and collected approximately 40 representative samples of sandstone and mudrock that were buried to 6–15 km. This depth range intersects the 10–50 km depth range of ETS events. My objectives are to quantify the water flow recorded in rocks of the Olympic Peninsula via petrographic, whole rock, and isotopic analyses to test the prediction that water release increases at ~10 km depth, creating fluid overpressure needed to trigger seismicity.
I calculated that on the Olympic Peninsula 1 km3 of 50% sandstone and 50% mudrock loses ~105 kg H2O/yr during burial from 6–14 km depth, comparable to the values expected from large-scale fluid budget models. Quartz veins that compose 0.5–1% of the Obstruction Peak site (~14 km burial depth) are important records of fluid flow quantity and origin. δ18O values of +11.8‰ to +15.2‰ indicate that vein H2O originated from metamorphic reactions. Flow recorded by 1 km3 of rock containing 0.5–1% quartz veins is >106 kg H2O/yr, comparable to the values 2 × 107 to 2 × 108 kg H2O/yr modeled at compositionally similar subduction zones to produce fluid overpressure conditions. I observed fibrous quartz veins, which also indicate fluid overpressure conditions were reached and support my H2O flow estimates. Therefore, Olympic Peninsula rocks at depths of ~10–14 km record dehydration and fluid overpressure large enough to trigger subduction zone seismicity.
"],"dc:identifier":["https://digitalcommons.cwu.edu/etd/1460"],"dc:subject":["sedimentary rocks","seismicity","Olympic Penninsula","Washington State","Dehydration reactions","Geophysics and Seismology","Hydrology","Mineral Physics"],"dc:title":["Fluid Budget of Metasedimentary Rocks from a Tertiary Accretionary Prism and Connections to Seismicity, Olympic Peninsula, Northwest Washington State"],"dc:type":["Text"],"thesis:degree_discipline":["Geological Sciences"],"thesis:degree_name":["Master of Science (MS)"]},"updated_at":"2026-07-24T01:37:54Z"}