Heat Flow and Fluid Flux in Cascadia's Seismogenic Zone

Abstract Body waveform inversion techniques are used to study the source parameters of four earthquakes occurring between 1937 and 1954 along the southern San Jacinto and Imperial faults (1937 Buck Ridge, 1940 Imperial Valley, 1942 Borrego Mountain, and 1954 Salada Wash events). All earthquakes had simple rupture histories with the exception of the 1940 Imperial Valley main shock, which consisted of at least four subevents whose relative locations indicate unilateral rupture toward the southeast. Earthquakes in regions of high heat flow (>80 mW/m2) had focal depths near the base of the seismogenic zone (8 to 10 km). The 1937 Buck Ridge earthquake, located in a region of lower heat flow, however, appears to have occurred at a shallow (3 ± 2 km) depth. The location, mechanism, and aftershock distribution for the 1942 Borrego Mountain earthquake suggest it could have occurred along the Split Mountain fault, a recently identified northeast-trending cross fault located between the Elsinore and Coyote Creek faults or along an unnamed fault that parallels the trend of the Coyote Creek fault. Moment and rupture length estimates obtained from this study agree well with estimates obtained in previous studies that used different data sets.

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Seismogenic zone temperatures and heat-flow anomalies in the To-nankai margin segment based on temperature data from IODP expedition 333 and thermal model

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2012.06.048 ◽

2012 ◽

Vol 349-350 ◽

pp. 171-185 ◽

Cited By ~ 20

Author(s):

Boris Marcaillou ◽

Pierre Henry ◽

Masataka Kinoshita ◽

Toshiya Kanamatsu ◽

Elizabeth Screaton ◽

...

Keyword(s):

Heat Flow ◽

Thermal Model ◽

Temperature Data ◽

Seismogenic Zone

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IODP Expedition 333: Return to Nankai Trough Subduction Inputs Sites and Coring of Mass Transport Deposits

Scientific Drilling ◽

10.5194/sd-14-4-2012 ◽

2012 ◽

Vol 14 ◽

pp. 4-17 ◽

Cited By ~ 7

Author(s):

P. Henry ◽

T. Kanamatsu ◽

K. T. Moe ◽

M. Strasser ◽

Keyword(s):

Heat Flow ◽

Mass Transport ◽

Nankai Trough ◽

Seismogenic Zone ◽

Ocean Drilling Program ◽

Flow Measurements ◽

Integrated Ocean Drilling Program ◽

Shikoku Basin ◽

Lower Temperature ◽

Mass Transport Deposits

Integrated Ocean Drilling Program (IODP) Expedition 333 returned to two sites drilled during IODP Expedition 322 on the ocean side of the Nankai Trough to pursue the characterization of the inputs to the Nankai subduction and seismogenic zone, as part of the Nankai Trough Seismogenic Experiment (NanTroSEIZE) multi-expedition project. Site C0011 is located at the seaward edge of the trench and Site C0012 on a basement high, Kashinozaki Knoll (Fig. 1). The main objectives of drilling again at these sites were to fill coring gaps in the upper part (<350 m) of the sedimentary sequence, to measure heat flow, and to core the oceanic basement to a greater depth on the Knoll. New results include the observation of a diagenetic boundary within the Shikoku Basin sediments that may be compared to one documented further west by ODP Legs 131, 190 and 196 but occurs here at a lower temperature. Borehole heat flow measurements confirm spatial variations in the Shikoku Basin that were indicated by short probe surveys. Heat flow variations between topographic highs and lows may be related to fluid convection within the basement. This expedition also included the objectives of the Nankai Trough Submarine LandSLIDE history (NanTroSLIDE) Ancillary Project Letter (APL) and cored at Site C0018 a pile of mass transport deposits on the footwall of the megasplay fault, a major out of sequence thrust that presumably slips coseismically during large subduction earthquakes. This brought new insight on the timing of these mass wasting events and on the deformation within the sliding slope sediments. doi:<a href="http://dx.doi.org/10.2204/iodp.sd.14.01.2012" target="_blank">10.2204/iodp.sd.14.01.2012</a>

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Contrasting seismogenic behaviors on the North Anatolian Fault in the Sea of Marmara

10.5194/egusphere-egu2020-10185 ◽

2020 ◽

Author(s):

Pierre Henry ◽

Céline Grall ◽

M Sinan Özeren ◽

Volkan Özbey ◽

Gülsen Uçarkus ◽

...

Keyword(s):

Heat Flow ◽

Sedimentary Cover ◽

Large Earthquake ◽

Fault Slip ◽

North Anatolian Fault ◽

Fault System ◽

Seismogenic Zone ◽

Sea Of Marmara ◽

The North

Since the 1999 Izmit-Kocaeli earthquake, the Main Marmara Fault (MMF) of the North Anatolian Fault system in the Sea of Marmara has been considered at an imminent risk for a large earthquake. Land geodesy has difficulties characterizing the distribution of interseismic loading, and hence of slip deficit, on the offshore faults, and notably on the Istanbul-Silivri segment of the NAF. The need to clarify the status of offshore fault segments has motivated seafloor monitoring experiments and marine geophysical and sedimentological studies, notably in the framework of EMSO consortium and MARSITE and MAREGAMI projects. Results from cross-disciplinary projects have shown that aseismic creep, spatially correlated to active gas venting at the seafloor, occurs on the Western segment of the MMF. This segment is also capable to large earthquake ruptures such as the 1912 event. On the eastern part of the Sea of Marmara, the Istanbul-Silivri and Prince Island segments appear essentially locked. Moreover, the base of the seismogenic zone and locking depth appears to shallow (from 15-20 to 10-15 km) from west to east.On one hand, we propose to further evaluate fault slip rates and distribution of locking ratio on individual fault segments using an elastic block model constrained by land geodesy data and marine observations (long-term fault slip rate estimates, local acoustic ranging results). On the other hand, we evaluate the temperature at the seismogenic depths by basin modelling. Results suggest that spatial variations of fault behavior in the Sea of Marmara may result from a combination of factors. First, thermogenic gas generation within the > 6 km thick sedimentary cover in the Western Sea of Marmara may contribute to unlock the shallow part of the fault by generating overpressures. Second, heterogeneity of the crust composition could be a factor as the North Anatolian Fault system follows the intra-pontide ophiolitic suture. For instance, long term post-seismic creep onland at Ismet Pa&#351;a has been related to the presence of serpentinite in the fault zone. Moreover, high-density magnetic bodies have been identified along the MMF. Third, varying thermal regimes between the Western and Eastern parts of the Sea of Marmara may account for variations in the seismogenic depths. Seafloor heat flow in the Sea of Marmara is strongly affected by sediment blanketing and basin modeling considering this process suggests that the crustal heat flow is about 20 mW/m2 higher in the eastern part than in western part of the Sea of Marmara. This difference may be explained by a more spread out crustal extension in the western Sea of Marmara.

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Coupled geophysical constraints on heat flow and fluid flux at a salt diapir

Geophysical Research Letters ◽

10.1029/2005gl024862 ◽

2005 ◽

Vol 32 (24) ◽

Cited By ~ 18

Author(s):

Matthew J. Hornbach ◽

Carolyn Ruppel ◽

Demian M. Saffer ◽

Cindy Lee Van Dover ◽

W. Steven Holbrook

Keyword(s):

Heat Flow ◽

Salt Diapir ◽

Fluid Flux

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Heat flow across the toe of accretionary prisms - The role of fluid flux

Geophysical Research Letters ◽

10.1029/93gl00331 ◽

1993 ◽

Vol 20 (8) ◽

pp. 659-662 ◽

Cited By ~ 8

Author(s):

Chi-yuen Wang ◽

Guoping Liang ◽

Yaolin Shi

Keyword(s):

Heat Flow ◽

Fluid Flux ◽

Accretionary Prisms

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The differences between the measured heat flow and BSR heat flow in the Shenhu gas hydrate drilling area, northern South China Sea

Energy Exploration & Exploitation ◽

10.1177/0144598718793907 ◽

2018 ◽

Vol 37 (2) ◽

pp. 756-769 ◽

Cited By ~ 2

Author(s):

Miao Dong ◽

Jian Zhang ◽

Xing Xu ◽

Shi-Guo Wu

Keyword(s):

Heat Flow ◽

Gas Hydrate ◽

Northern South China Sea ◽

Geothermal Gradient ◽

Topographic Effects ◽

Fluid Flux ◽

Flow Measurements ◽

Upward Migration ◽

Bottom Simulating Reflector ◽

The Impact

Temperature is an important factor that affects the stability of a gas hydrate. To investigate the geothermal characteristics in the gas hydrate drilling area, heat flow measurements were performed in the surrounding area of the SH2 well. The measured heat flow was compared with the bottom simulating reflector heat flow, which was calculated by using the depth of the bottom simulating reflector in the seismic data. Combined with the geological background of the Shenhu drilling area, we analyzed the reasons for the differences between the measured heat flow and the bottom simulating reflector heat flow. In addition to analyzing the differences caused by the calculation parameters, we calculated the 3-D topographic effects on the measured heat flow by using the finite element numerical simulation method. The results show that the measured heat flow was seriously affected by the topography and produced a −50–30% error in the study area. After terrain correction of the measured heat flow, we found that the data were greater than the bottom simulating reflector heat flow at almost all sites. Therefore, we considered the impact of fluid activity and calculated the relationship among the thickness of the gas hydrate stability zone, the fluid flux and the heat flow. The results show that when the base of the bottom simulating reflector was at a certain depth, the geothermal gradient increased with the increasing upward migration of the fluid flux. Therefore, when upward fluid migration is present, the measured heat flow in the seafloor sediments is greater than the heat flow in the deep layers. In general, we showed that the influences of the topography and fluid activity are the main factors leading to the inconsistency between the bottom simulating reflector heat flow and the measured heat flow in the Shenhu gas hydrate drilling area.

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How wide is the seismogenic zone of the Lesser Antilles forearc?

BSGF - Earth Sciences Bulletin ◽

10.2113/gssgfbull.184.1-2.47 ◽

2013 ◽

Vol 184 (1-2) ◽

pp. 47-59 ◽

Cited By ~ 4

Author(s):

Marc-André Gutscher ◽

Graham K. Westbrook ◽

Boris Marcaillou ◽

David Graindorge ◽

Audrey Gailler ◽

...

Keyword(s):

Heat Flow ◽

Numerical Models ◽

Thermal Structure ◽

Lesser Antilles ◽

Seismogenic Zone ◽

Segment Length ◽

Accretionary Wedge ◽

The South ◽

Maximum Width ◽

Minimum Width

Abstract The Lesser Antilles subduction zone has produced no recent strong thrust earthquakes, making it difficult to quantify the seismic hazard from such events. The Lesser Antilles arc has a low subduction rate and an accretionary wedge that is very wide at its southern end. To investigate the effect of the wedge on seismogenesis, numerical models of forearc thermal structure were constructed along six transects perpendicular to the arc in order to determine the thermally predicted width of the seismogenic zone. The geometry of each section is constrained by published seismic profiles and crustal models derived from gravity and seismic data and by earthquake hypocenters at depth. A major constraint on the deep part of the model is that mantle temperature beneath the volcanic arc should achieve a temperature of 1,100°C to generate partial melts. Predicted surface heat flow is compared to the available heat flow observations. Thermal modeling results indicate a systematic southward increase in the width of the seismogenic zone, more than doubling in width from north to south and corresponding to a dramatic southward increase in forearc width (distance from the arc to the deformation front of the accretionary wedge). The minimum width of the seismogenic zone (distance between the intersections of the subduction interface with the 150°C and 350°C isotherms) increases from about 80 km, north of 16°N, to 230 km, at 13°N. The maximum width (between the 100°C and 450°C isotherms) ranges from about 150 km in the north to up to 320 km in the south. This large variation in the width of the seismogenic zone is a consequence of the increasing width of the accretionary wedge to the south, caused by the increased thickness of sediment on the subducting plate. There is good agreement between the thermally predicted seismogenic limits and the sparse distribution of recorded thrust earthquakes, which are observed only in the northern portion of the arc. Possible scenarios for mega-thrust earthquakes are discussed. Depending on the segment length (along-strike) of the rupture plane, the occurrence of an event of magnitude 8–9 cannot be excluded.

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