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Thomas M Brocher - One of the best experts on this subject based on the ideXlab platform.
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earthquakes generated from Bedding Plane parallel reverse faults above an active wedge thrust seattle fault zone
Geological Society of America Bulletin, 2008Co-Authors: Harvey M Kelsey, Brian L Sherrod, Alan R Nelson, Thomas M BrocherAbstract:A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, Bedding-Plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900–930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the backthrust. This earthquake also included slip on some of the <6-km-deep north-side-up, Bedding-Plane reverse faults. At locales where the north-side-up reverse faults intersect the Puget Sound coast, an earthquake a few centuries earlier than the A.D. 900–930 regional uplift only uplifted areas within hundreds of meters north of the reverse faults. We infer that the Bedding-Plane reverse faults are seismogenic because shore platforms near the reverse faults have been abruptly uplifted during earthquakes when other shorelines in the Seattle fault zone were unaffected. Faults of the Seattle fault zone therefore can both produce regional uplift earthquakes, with or without surface displacement on the reverse faults, and produce earthquakes that rupture the Bedding-Plane reverse faults causing fault scarps and uplift localized to hundreds of meters north of these faults. This latter type of earthquake has occurred at least twice and perhaps three times in the late Holocene, and all these earthquakes preceded the regional coseismic uplift of A.D. 900–930. To account for the paleoseismic observations, we propose that the Seattle fault zone is a wedge thrust, with the leading edge being a fault-bend, wedge thrust fold. The active axial surface of the wedge thrust fold is pinned at the tip of the wedge, and a steeply north-dipping sequence of Tertiary sediment forms the south limb of the wedge thrust fold. Some of these steeply north-dipping, Bedding-Plane surfaces are seismogenic reverse faults that produce scarps. Earthquakes on the wedge thrust produce the regional coseismic uplift events, and earthquakes within the faultbend fold cause the local uplift earthquakes. Thus, Bedding-Plane faults can rupture during earthquakes when the wedge thrust does not rupture but instead continues to accumulate seismic energy.
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earthquakes generated from Bedding Plane parallel reverse faults above an active wedge thrust seattle fault zone
Geological Society of America Bulletin, 2008Co-Authors: Harvey M Kelsey, Brian L Sherrod, Alan R Nelson, Thomas M BrocherAbstract:A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, Bedding-Plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900–930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the backthrust. This earthquake also included slip on some of the <6-km-deep north-side-up, Bedding-Plane reverse faults. At locales where the north-side-up reverse faults intersect the Puget Sound coast, an earthquake a few centuries earlier than the A.D. 900–930 regional uplift only uplifted areas within hundreds of meters north of the reverse faults. We infer that the Bedding-Plane reverse faults are seismogenic because shore platforms near the reverse faults have been abruptly uplifted during earthquakes when other shorelines in the Seattle fault zone were unaffected. Faults of the Seattle fault zone therefore can both produce regional uplift earthquakes, with or without surface displacement on the reverse faults, and produce earthquakes that rupture the Bedding-Plane reverse faults causing fault scarps and uplift localized to hundreds of meters north of these faults. This latter type of earthquake has occurred at least twice and perhaps three times in the late Holocene, and all these earthquakes preceded the regional coseismic uplift of A.D. 900–930. To account for the paleoseismic observations, we propose that the Seattle fault zone is a wedge thrust, with the leading edge being a fault-bend, wedge thrust fold. The active axial surface of the wedge thrust fold is pinned at the tip of the wedge, and a steeply north-dipping sequence of Tertiary sediment forms the south limb of the wedge thrust fold. Some of these steeply north-dipping, Bedding-Plane surfaces are seismogenic reverse faults that produce scarps. Earthquakes on the wedge thrust produce the regional coseismic uplift events, and earthquakes within the faultbend fold cause the local uplift earthquakes. Thus, Bedding-Plane faults can rupture during earthquakes when the wedge thrust does not rupture but instead continues to accumulate seismic energy.
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Earthquakes generated from Bedding Plane-parallel reverse faults above an active wedge thrust, Seattle fault zone
Geological Society of America Bulletin, 2008Co-Authors: Harvey M Kelsey, Brian L Sherrod, Alan R Nelson, Thomas M BrocherAbstract:A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, Bedding-Plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900–930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the backthrust. This earthquake also included slip on some of the
Harvey M Kelsey - One of the best experts on this subject based on the ideXlab platform.
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earthquakes generated from Bedding Plane parallel reverse faults above an active wedge thrust seattle fault zone
Geological Society of America Bulletin, 2008Co-Authors: Harvey M Kelsey, Brian L Sherrod, Alan R Nelson, Thomas M BrocherAbstract:A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, Bedding-Plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900–930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the backthrust. This earthquake also included slip on some of the <6-km-deep north-side-up, Bedding-Plane reverse faults. At locales where the north-side-up reverse faults intersect the Puget Sound coast, an earthquake a few centuries earlier than the A.D. 900–930 regional uplift only uplifted areas within hundreds of meters north of the reverse faults. We infer that the Bedding-Plane reverse faults are seismogenic because shore platforms near the reverse faults have been abruptly uplifted during earthquakes when other shorelines in the Seattle fault zone were unaffected. Faults of the Seattle fault zone therefore can both produce regional uplift earthquakes, with or without surface displacement on the reverse faults, and produce earthquakes that rupture the Bedding-Plane reverse faults causing fault scarps and uplift localized to hundreds of meters north of these faults. This latter type of earthquake has occurred at least twice and perhaps three times in the late Holocene, and all these earthquakes preceded the regional coseismic uplift of A.D. 900–930. To account for the paleoseismic observations, we propose that the Seattle fault zone is a wedge thrust, with the leading edge being a fault-bend, wedge thrust fold. The active axial surface of the wedge thrust fold is pinned at the tip of the wedge, and a steeply north-dipping sequence of Tertiary sediment forms the south limb of the wedge thrust fold. Some of these steeply north-dipping, Bedding-Plane surfaces are seismogenic reverse faults that produce scarps. Earthquakes on the wedge thrust produce the regional coseismic uplift events, and earthquakes within the faultbend fold cause the local uplift earthquakes. Thus, Bedding-Plane faults can rupture during earthquakes when the wedge thrust does not rupture but instead continues to accumulate seismic energy.
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earthquakes generated from Bedding Plane parallel reverse faults above an active wedge thrust seattle fault zone
Geological Society of America Bulletin, 2008Co-Authors: Harvey M Kelsey, Brian L Sherrod, Alan R Nelson, Thomas M BrocherAbstract:A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, Bedding-Plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900–930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the backthrust. This earthquake also included slip on some of the <6-km-deep north-side-up, Bedding-Plane reverse faults. At locales where the north-side-up reverse faults intersect the Puget Sound coast, an earthquake a few centuries earlier than the A.D. 900–930 regional uplift only uplifted areas within hundreds of meters north of the reverse faults. We infer that the Bedding-Plane reverse faults are seismogenic because shore platforms near the reverse faults have been abruptly uplifted during earthquakes when other shorelines in the Seattle fault zone were unaffected. Faults of the Seattle fault zone therefore can both produce regional uplift earthquakes, with or without surface displacement on the reverse faults, and produce earthquakes that rupture the Bedding-Plane reverse faults causing fault scarps and uplift localized to hundreds of meters north of these faults. This latter type of earthquake has occurred at least twice and perhaps three times in the late Holocene, and all these earthquakes preceded the regional coseismic uplift of A.D. 900–930. To account for the paleoseismic observations, we propose that the Seattle fault zone is a wedge thrust, with the leading edge being a fault-bend, wedge thrust fold. The active axial surface of the wedge thrust fold is pinned at the tip of the wedge, and a steeply north-dipping sequence of Tertiary sediment forms the south limb of the wedge thrust fold. Some of these steeply north-dipping, Bedding-Plane surfaces are seismogenic reverse faults that produce scarps. Earthquakes on the wedge thrust produce the regional coseismic uplift events, and earthquakes within the faultbend fold cause the local uplift earthquakes. Thus, Bedding-Plane faults can rupture during earthquakes when the wedge thrust does not rupture but instead continues to accumulate seismic energy.
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Earthquakes generated from Bedding Plane-parallel reverse faults above an active wedge thrust, Seattle fault zone
Geological Society of America Bulletin, 2008Co-Authors: Harvey M Kelsey, Brian L Sherrod, Alan R Nelson, Thomas M BrocherAbstract:A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, Bedding-Plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900–930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the backthrust. This earthquake also included slip on some of the
Brian L Sherrod - One of the best experts on this subject based on the ideXlab platform.
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earthquakes generated from Bedding Plane parallel reverse faults above an active wedge thrust seattle fault zone
Geological Society of America Bulletin, 2008Co-Authors: Harvey M Kelsey, Brian L Sherrod, Alan R Nelson, Thomas M BrocherAbstract:A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, Bedding-Plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900–930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the backthrust. This earthquake also included slip on some of the <6-km-deep north-side-up, Bedding-Plane reverse faults. At locales where the north-side-up reverse faults intersect the Puget Sound coast, an earthquake a few centuries earlier than the A.D. 900–930 regional uplift only uplifted areas within hundreds of meters north of the reverse faults. We infer that the Bedding-Plane reverse faults are seismogenic because shore platforms near the reverse faults have been abruptly uplifted during earthquakes when other shorelines in the Seattle fault zone were unaffected. Faults of the Seattle fault zone therefore can both produce regional uplift earthquakes, with or without surface displacement on the reverse faults, and produce earthquakes that rupture the Bedding-Plane reverse faults causing fault scarps and uplift localized to hundreds of meters north of these faults. This latter type of earthquake has occurred at least twice and perhaps three times in the late Holocene, and all these earthquakes preceded the regional coseismic uplift of A.D. 900–930. To account for the paleoseismic observations, we propose that the Seattle fault zone is a wedge thrust, with the leading edge being a fault-bend, wedge thrust fold. The active axial surface of the wedge thrust fold is pinned at the tip of the wedge, and a steeply north-dipping sequence of Tertiary sediment forms the south limb of the wedge thrust fold. Some of these steeply north-dipping, Bedding-Plane surfaces are seismogenic reverse faults that produce scarps. Earthquakes on the wedge thrust produce the regional coseismic uplift events, and earthquakes within the faultbend fold cause the local uplift earthquakes. Thus, Bedding-Plane faults can rupture during earthquakes when the wedge thrust does not rupture but instead continues to accumulate seismic energy.
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earthquakes generated from Bedding Plane parallel reverse faults above an active wedge thrust seattle fault zone
Geological Society of America Bulletin, 2008Co-Authors: Harvey M Kelsey, Brian L Sherrod, Alan R Nelson, Thomas M BrocherAbstract:A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, Bedding-Plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900–930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the backthrust. This earthquake also included slip on some of the <6-km-deep north-side-up, Bedding-Plane reverse faults. At locales where the north-side-up reverse faults intersect the Puget Sound coast, an earthquake a few centuries earlier than the A.D. 900–930 regional uplift only uplifted areas within hundreds of meters north of the reverse faults. We infer that the Bedding-Plane reverse faults are seismogenic because shore platforms near the reverse faults have been abruptly uplifted during earthquakes when other shorelines in the Seattle fault zone were unaffected. Faults of the Seattle fault zone therefore can both produce regional uplift earthquakes, with or without surface displacement on the reverse faults, and produce earthquakes that rupture the Bedding-Plane reverse faults causing fault scarps and uplift localized to hundreds of meters north of these faults. This latter type of earthquake has occurred at least twice and perhaps three times in the late Holocene, and all these earthquakes preceded the regional coseismic uplift of A.D. 900–930. To account for the paleoseismic observations, we propose that the Seattle fault zone is a wedge thrust, with the leading edge being a fault-bend, wedge thrust fold. The active axial surface of the wedge thrust fold is pinned at the tip of the wedge, and a steeply north-dipping sequence of Tertiary sediment forms the south limb of the wedge thrust fold. Some of these steeply north-dipping, Bedding-Plane surfaces are seismogenic reverse faults that produce scarps. Earthquakes on the wedge thrust produce the regional coseismic uplift events, and earthquakes within the faultbend fold cause the local uplift earthquakes. Thus, Bedding-Plane faults can rupture during earthquakes when the wedge thrust does not rupture but instead continues to accumulate seismic energy.
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Earthquakes generated from Bedding Plane-parallel reverse faults above an active wedge thrust, Seattle fault zone
Geological Society of America Bulletin, 2008Co-Authors: Harvey M Kelsey, Brian L Sherrod, Alan R Nelson, Thomas M BrocherAbstract:A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, Bedding-Plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900–930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the backthrust. This earthquake also included slip on some of the
Alan R Nelson - One of the best experts on this subject based on the ideXlab platform.
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earthquakes generated from Bedding Plane parallel reverse faults above an active wedge thrust seattle fault zone
Geological Society of America Bulletin, 2008Co-Authors: Harvey M Kelsey, Brian L Sherrod, Alan R Nelson, Thomas M BrocherAbstract:A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, Bedding-Plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900–930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the backthrust. This earthquake also included slip on some of the <6-km-deep north-side-up, Bedding-Plane reverse faults. At locales where the north-side-up reverse faults intersect the Puget Sound coast, an earthquake a few centuries earlier than the A.D. 900–930 regional uplift only uplifted areas within hundreds of meters north of the reverse faults. We infer that the Bedding-Plane reverse faults are seismogenic because shore platforms near the reverse faults have been abruptly uplifted during earthquakes when other shorelines in the Seattle fault zone were unaffected. Faults of the Seattle fault zone therefore can both produce regional uplift earthquakes, with or without surface displacement on the reverse faults, and produce earthquakes that rupture the Bedding-Plane reverse faults causing fault scarps and uplift localized to hundreds of meters north of these faults. This latter type of earthquake has occurred at least twice and perhaps three times in the late Holocene, and all these earthquakes preceded the regional coseismic uplift of A.D. 900–930. To account for the paleoseismic observations, we propose that the Seattle fault zone is a wedge thrust, with the leading edge being a fault-bend, wedge thrust fold. The active axial surface of the wedge thrust fold is pinned at the tip of the wedge, and a steeply north-dipping sequence of Tertiary sediment forms the south limb of the wedge thrust fold. Some of these steeply north-dipping, Bedding-Plane surfaces are seismogenic reverse faults that produce scarps. Earthquakes on the wedge thrust produce the regional coseismic uplift events, and earthquakes within the faultbend fold cause the local uplift earthquakes. Thus, Bedding-Plane faults can rupture during earthquakes when the wedge thrust does not rupture but instead continues to accumulate seismic energy.
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earthquakes generated from Bedding Plane parallel reverse faults above an active wedge thrust seattle fault zone
Geological Society of America Bulletin, 2008Co-Authors: Harvey M Kelsey, Brian L Sherrod, Alan R Nelson, Thomas M BrocherAbstract:A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, Bedding-Plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900–930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the backthrust. This earthquake also included slip on some of the <6-km-deep north-side-up, Bedding-Plane reverse faults. At locales where the north-side-up reverse faults intersect the Puget Sound coast, an earthquake a few centuries earlier than the A.D. 900–930 regional uplift only uplifted areas within hundreds of meters north of the reverse faults. We infer that the Bedding-Plane reverse faults are seismogenic because shore platforms near the reverse faults have been abruptly uplifted during earthquakes when other shorelines in the Seattle fault zone were unaffected. Faults of the Seattle fault zone therefore can both produce regional uplift earthquakes, with or without surface displacement on the reverse faults, and produce earthquakes that rupture the Bedding-Plane reverse faults causing fault scarps and uplift localized to hundreds of meters north of these faults. This latter type of earthquake has occurred at least twice and perhaps three times in the late Holocene, and all these earthquakes preceded the regional coseismic uplift of A.D. 900–930. To account for the paleoseismic observations, we propose that the Seattle fault zone is a wedge thrust, with the leading edge being a fault-bend, wedge thrust fold. The active axial surface of the wedge thrust fold is pinned at the tip of the wedge, and a steeply north-dipping sequence of Tertiary sediment forms the south limb of the wedge thrust fold. Some of these steeply north-dipping, Bedding-Plane surfaces are seismogenic reverse faults that produce scarps. Earthquakes on the wedge thrust produce the regional coseismic uplift events, and earthquakes within the faultbend fold cause the local uplift earthquakes. Thus, Bedding-Plane faults can rupture during earthquakes when the wedge thrust does not rupture but instead continues to accumulate seismic energy.
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Earthquakes generated from Bedding Plane-parallel reverse faults above an active wedge thrust, Seattle fault zone
Geological Society of America Bulletin, 2008Co-Authors: Harvey M Kelsey, Brian L Sherrod, Alan R Nelson, Thomas M BrocherAbstract:A key question in earthquake hazard analysis is whether individual faults within fault zones represent independent seismic sources. For the Seattle fault zone, an upper plate structure within the Cascadia convergent margin, evaluating seismic hazard requires understanding how north-side-up, Bedding-Plane reverse faults, which generate late Holocene fault scarps, interact with the north-vergent master-ramp thrust and overlying backthrust of the fault zone. A regional uplift at A.D. 900–930 involved an earthquake that nucleated at depth and included slip on both the master-ramp thrust and the backthrust. This earthquake also included slip on some of the
Keith Priestley - One of the best experts on this subject based on the ideXlab platform.
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the 1994 sefidabeh earthquakes in eastern iran blind thrusting and Bedding Plane slip on a growing anticline and active tectonics of the sistan suture zone
Geophysical Journal International, 2000Co-Authors: Manuel Berberian, James Jackson, M Qorashi, M Talebian, Mohammad Mahdi Khatib, Keith PriestleyAbstract:Summary In 1994 a sequence of five earthquakes with Mw 5.5–6.2 occurred in the Sistan belt of eastern Iran, all of them involving motion on blind thrusts with centroid depths of 5–10 km. Coseismic ruptures at the surface involved Bedding-Plane slip on a growing hanging-wall anticline displaying geomorphological evidence of uplift and lateral propagation. The 1994 earthquakes were associated with a NW-trending thrust system that splays off the northern termination of a major N–S right-lateral strike-slip fault. Elevation changes along the anticline ridge suggest that displacement on the underlying thrust dies out to the NW, away from its intersection with the strike-slip fault. This is a common fault configuration in eastern Iran and accommodates oblique NE–SW shortening across the N–S deforming zone, probably by anticlockwise rotations about a vertical axis. This style of fault kinematics may be transitional to a more evolved state that involves partitioning of the strike-slip and convergent motion onto separate subparallel faults.
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The 1994 Sefidabeh earthquakes in eastern Iran: blind thrusting and Bedding‐Plane slip on a growing anticline, and active tectonics of the Sistan suture zone
Geophysical Journal International, 2000Co-Authors: Manuel Berberian, James Jackson, M Qorashi, M Talebian, Mohammad Mahdi Khatib, Keith PriestleyAbstract:Summary In 1994 a sequence of five earthquakes with Mw 5.5–6.2 occurred in the Sistan belt of eastern Iran, all of them involving motion on blind thrusts with centroid depths of 5–10 km. Coseismic ruptures at the surface involved Bedding-Plane slip on a growing hanging-wall anticline displaying geomorphological evidence of uplift and lateral propagation. The 1994 earthquakes were associated with a NW-trending thrust system that splays off the northern termination of a major N–S right-lateral strike-slip fault. Elevation changes along the anticline ridge suggest that displacement on the underlying thrust dies out to the NW, away from its intersection with the strike-slip fault. This is a common fault configuration in eastern Iran and accommodates oblique NE–SW shortening across the N–S deforming zone, probably by anticlockwise rotations about a vertical axis. This style of fault kinematics may be transitional to a more evolved state that involves partitioning of the strike-slip and convergent motion onto separate subparallel faults.