Possible control of subduction zone slow-earthquake periodicity by silica enrichment.
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| Title: | Possible control of subduction zone slow-earthquake periodicity by silica enrichment. |
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| Authors: | Audet, Pascal, Bürgmann, Roland |
| Source: | Nature. 6/19/2014, Vol. 510 Issue 7505, p389-392. 4p. |
| Subjects: | Subduction zones, Earthquakes, Tremor, Fluid pressure, Mineralization, Permeability |
| Abstract: | Seismic and geodetic observations in subduction zone forearcs indicate that slow earthquakes, including episodic tremor and slip, recur at intervals of less than six months to more than two years. In Cascadia, slow slip is segmented along strike and tremor data show a gradation from large, infrequent slip episodes to small, frequent slip events with increasing depth of the plate interface. Observations and models of slow slip and tremor require the presence of near-lithostatic pore-fluid pressures in slow-earthquake source regions; however, direct evidence of factors controlling the variability in recurrence times is elusive. Here we compile seismic data from subduction zone forearcs exhibiting recurring slow earthquakes and show that the average ratio of compressional (P)-wave velocity to shear (S)-wave velocity (vP/vS) of the overlying forearc crust ranges between 1.6 and 2.0 and is linearly related to the average recurrence time of slow earthquakes. In northern Cascadia, forearc vP/vS values decrease with increasing depth of the plate interface and with decreasing tremor-episode recurrence intervals. Low vP/vS values require a large addition of quartz in a mostly mafic forearc environment. We propose that silica enrichment varying from 5 per cent to 15 per cent by volume from slab-derived fluids and upward mineralization in quartz veins can explain the range of observed vP/vS values as well as the downdip decrease in vP/vS. The solubility of silica depends on temperature, and deposition prevails near the base of the forearc crust. We further propose that the strong temperature dependence of healing and permeability reduction in silica-rich fault gouge via dissolution-precipitation creep can explain the reduction in tremor recurrence time with progressive silica enrichment. Lower gouge permeability at higher temperatures leads to faster fluid overpressure development and low effective fault-normal stress, and therefore shorter recurrence times. Our results also agree with numerical models of slip stabilization under fault zone dilatancy strengthening caused by decreasing fluid pressure as pore space increases. This implies that temperature-dependent silica deposition, permeability reduction and fluid overpressure development control dilatancy and slow-earthquake behaviour. [ABSTRACT FROM AUTHOR] |
| Copyright of Nature is the property of Springer Nature and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Psychology and Behavioral Sciences Collection |
| FullText | Links: – Type: pdflink Text: Availability: 0 |
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| Header | DbId: pbh DbLabel: Psychology and Behavioral Sciences Collection An: 96771793 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Possible control of subduction zone slow-earthquake periodicity by silica enrichment. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Audet%2C+Pascal%22">Audet, Pascal</searchLink><br /><searchLink fieldCode="AR" term="%22Bürgmann%2C+Roland%22">Bürgmann, Roland</searchLink> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Nature%22">Nature</searchLink>. 6/19/2014, Vol. 510 Issue 7505, p389-392. 4p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Subduction+zones%22">Subduction zones</searchLink><br /><searchLink fieldCode="DE" term="%22Earthquakes%22">Earthquakes</searchLink><br /><searchLink fieldCode="DE" term="%22Tremor%22">Tremor</searchLink><br /><searchLink fieldCode="DE" term="%22Fluid+pressure%22">Fluid pressure</searchLink><br /><searchLink fieldCode="DE" term="%22Mineralization%22">Mineralization</searchLink><br /><searchLink fieldCode="DE" term="%22Permeability%22">Permeability</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Seismic and geodetic observations in subduction zone forearcs indicate that slow earthquakes, including episodic tremor and slip, recur at intervals of less than six months to more than two years. In Cascadia, slow slip is segmented along strike and tremor data show a gradation from large, infrequent slip episodes to small, frequent slip events with increasing depth of the plate interface. Observations and models of slow slip and tremor require the presence of near-lithostatic pore-fluid pressures in slow-earthquake source regions; however, direct evidence of factors controlling the variability in recurrence times is elusive. Here we compile seismic data from subduction zone forearcs exhibiting recurring slow earthquakes and show that the average ratio of compressional (P)-wave velocity to shear (S)-wave velocity (vP/vS) of the overlying forearc crust ranges between 1.6 and 2.0 and is linearly related to the average recurrence time of slow earthquakes. In northern Cascadia, forearc vP/vS values decrease with increasing depth of the plate interface and with decreasing tremor-episode recurrence intervals. Low vP/vS values require a large addition of quartz in a mostly mafic forearc environment. We propose that silica enrichment varying from 5 per cent to 15 per cent by volume from slab-derived fluids and upward mineralization in quartz veins can explain the range of observed vP/vS values as well as the downdip decrease in vP/vS. The solubility of silica depends on temperature, and deposition prevails near the base of the forearc crust. We further propose that the strong temperature dependence of healing and permeability reduction in silica-rich fault gouge via dissolution-precipitation creep can explain the reduction in tremor recurrence time with progressive silica enrichment. Lower gouge permeability at higher temperatures leads to faster fluid overpressure development and low effective fault-normal stress, and therefore shorter recurrence times. Our results also agree with numerical models of slip stabilization under fault zone dilatancy strengthening caused by decreasing fluid pressure as pore space increases. This implies that temperature-dependent silica deposition, permeability reduction and fluid overpressure development control dilatancy and slow-earthquake behaviour. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Nature is the property of Springer Nature and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1038/nature13391 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 4 StartPage: 389 Subjects: – SubjectFull: Subduction zones Type: general – SubjectFull: Earthquakes Type: general – SubjectFull: Tremor Type: general – SubjectFull: Fluid pressure Type: general – SubjectFull: Mineralization Type: general – SubjectFull: Permeability Type: general Titles: – TitleFull: Possible control of subduction zone slow-earthquake periodicity by silica enrichment. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Audet, Pascal – PersonEntity: Name: NameFull: Bürgmann, Roland IsPartOfRelationships: – BibEntity: Dates: – D: 19 M: 06 Text: 6/19/2014 Type: published Y: 2014 Identifiers: – Type: issn-print Value: 00280836 Numbering: – Type: volume Value: 510 – Type: issue Value: 7505 Titles: – TitleFull: Nature Type: main |
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