Heat flow, Hawaiian area

Six hundred and eighty-seven heat flow data from more than 780 individual determinations and estimations were compiled. Of these, 634 data were analyzed. The range of the present heat flow per unit area is approximately 0 to 8 •cal/cm a sec. The world's arithmetic mean is 1.62, and the standard deviation of a datum is 1.21. The data do not seem to form any simple distribution. Since the sampling is poor and biased, a weighted mean technique is developed. On the basis of three assumptions, the world's average heat flow per unit area was found to be 1.5 ___ 10 per cent at 95 per cent confidence. This is significantly higher than the value 1,2 suggested in 1954. There is no simple dependence of heat flow per unit area on latitude and longitude. A spherical harmonic analysis indicates that all the coefficients of the harmonics are at least an order of magnitude less than the mean of about 1.5. Heat flow and geological parameters, as well as dif•culties in heat flow research and sources of heat, are briefly discussed. The purpose of this study is to summarize all the available data in a comprehensive list with extensive bibliographies and to set up computer programs for data analysis that can be used in the future.

Journal of Geophysical Research: Solid Earth, 2013

We review marine heat flow data along the Nankai Trough and show that observations >30 km seaward of the deformation front are 20% below conductive predictions (129-94 mW m À2) but consistent with the global heat flow average for oceanic crust of the same age (16-28 Ma). Heat flow values ≤30 km seaward of the deformation front are generally 20% higher than conductive predictions. This heat flow pattern is consistent with the advection of heat by fluid flow in the subducting oceanic crust and explains both the high heat flux in the vicinity of the trench, >200 and >140 mW m À2 , and steep landward declines to values of approximately 60 mW m À2 over distances of 65 and 50 km along the Muroto and Kumano transects, respectively. Along the Ashizuri transect, the lack of heat flow data precludes a definitive interpretation. We conclude that fluid flow in the subducting oceanic crust leads to temperatures that are generally 25 C higher near the toe of the margin wedge and 50-100 C lower near the downdip limit of the seismogenic zone than estimated by purely conductive models.

Physics of the Earth and Planetary Interiors, 2005

We calculated statistical average of thermal data to speculate regional thermal structure of the forearc area of the Japanese Islands. The three thermal statistical averages show a difference of a high thermal regime in the western part of forearc inner zone and a low in the Kanto forearc outer zone. The Kanto zone marks 18 K km −1 for mean geothermal gradient, 44 mW m −2 for mean heat flow, while the western inner zone shows 27 K km −1 for mean geothermal gradient, 63 mW m −2 for mean heat flow. The geothermal gradients of the Nobi Plain and the Osaka Plain in the western inner zone are 29 and 36 K km −1 , respectively, while the value of the Kanto Plain in the Kanto zone is 21 K km −1. Taking account of the effect of accumulation of sediments, we see the difference in the thermal regime between the plains and conclude that the difference is significant. Heat flux in the crust depends on the volume of granite rich in radioactive elements. There are few granitic rocks in the Kanto zone, while granitic rocks are dominant in the western inner zone. The heat flow of 20 mW m −2 is attributed to the granitic rocks of about 8 km in thickness. There are two oceanic plate subductions of the Pacific plate and the Philippine Sea plate under the Kanto zone, while only the Philippine Sea plate has been subducting under the western inner zone. The model simulation based on thermal and subduction model shows a heat flow ranging 50-60 mW m −2 in the southwest Japan forarc area and a low value of about 20 mW m −2 in the northeast Japan forearc area. The heat flux from the cooling oceanic lithosphere depends on the age of plate. The Shikoku Basin, a part of the Philippine Sea plate, off the western inner zone is 15-30 Ma, while the Pacific plate off the Kanto zone is 122-132 Ma. Theoretically, heat flux values of 15 and 50 Ma oceanic plates range 60-120 mW m −2 and those of 122-132 Ma could be about 10 mW m −2. If the heat flux contribution from the Philippine Sea plate under the Kanto zone is smaller than the plate under the western inner zone, there could be a thermal regime difference in order of several tens of mW m −2. Conclusively, the cause of the difference of heat flux could be the uneven granitic rocks distribution and/or the difference of heat flux between the two subducting plate.

Eos, Transactions American Geophysical Union, 1996

Traditional probes designed to measure heat flow in oceanic crust only yield accu rate measurements where thick sediment thermally isolates igneous basement rocks from seawater. Since most regions of younger crust lack this sediment cover, meas uring crustal heat flow in these areas presents a challenge. A thermal blanket system that simulates this sediment cover and allows measurements to be taken in bare rock areas was recently developed and tested, and the results look promising.

Geothermics, 1993

Temperature measurements on shallow vertical profiles undertaken on Matthews and Hunter volcanoes of the New Hebrides arc (SW Pacific) demonstrate the absence of both unsteady and steady conductive abnormal flux at the location of the studied profiles. The reasons for this absence are explained in terms of limits in depth or magnitude for possible sources of heat inside the volcanoes. It implies that the magma chamber is of rather limited extent. This type of flux measurement has a low cost and it will be possible to implant a series of such temperature profiles on an edifice in order to obtain a map of the flux that could be widely used for the location of heat sources.

Bulletin of Volcanology, 1999

To test the potential of heat flux prospecting in active volcanic areas using shallow temperature data taken along vertical profiles, we carried out two thermal profile surveys, one not far from Yasur cone on Tanna Island, and another inside the caldera of Ambrym (New Hebrides arc, southwestern Pacific). The basic steady heat flux of internal volcanic origin was determined, taking into account both conductive and convective heat transfers. At both locations there exists, over small distances, significant differences in the heat flux. These differences correspond to shallow sources of heat. The use of a network of vertical profiles allowed: (a) heat flux mapping; (b) location of shallow volcanic heat sources; and (c) observation of the detailed structure of the heat release at quiescent but active volcanoes.

Journal of Geophysical Research: Solid Earth, 2014

Geophysical Journal International, 1990

Multipenetration heat flow measurements have been made at four sites in deep basins of the west-central Pacific Ocean: the West Mariana Basin, Central Mariana Basin, Nauru Basin and Central Pacific Basin. The final heat flows are, respectively, 46.6 f 0.5, 49.4 f 0.2, 44.2 f 0.9 and 49.5 f 1.1 mW m-*. Each site was surveyed by

1999

To test the potential of heat flux prospecting in active volcanic areas using shallow temperature data taken along vertical profiles, we carried out two thermal profile surveys, one not far from Yasur cone on Tanna Island, and another inside the caldera of Ambrym (New Hebrides arc, southwestern Pacific). The basic steady heat flux of internal volcanic origin was determined, taking into account both conductive and convective heat transfers. At both locations there exists, over small distances, significant differences in the heat flux. These differences correspond to shallow sources of heat. The use of a network of vertical profiles allowed: (a) heat flux mapping; (b) location of shallow volcanic heat sources; and (c) observation of the detailed structure of the heat release at quiescent but active volcanoes.

Dìqiú kēxué jíkān, 2001

Detailed heat flow measurements were carried out around the ODP contingency drilling site KS-1(24°48'N,122°30'E) located on the southern slope of the southwestern end of the Okinawa Trough. A total of 26 heat flow values were obtained. Within about 10 km of the site, the heat flow is lower than 50 mW!m2• Heat flow increases southward to about 65 mW/m2 on the south edge of the trough. Due to the extraordinarily high sedimenta tion rates, the sedimentation-corrected heat flow values have increased by as much as 76 % , so only the most recent surface sedimentation effects are considered. Distribution of heat flow patterns shows that high heat flow values are associated with igneous activities and are observed in both the northern and southern flank and the western end of the Okinawa Trough. Heat flow values in the E-W trending centraJ rift zone, on the other hand, appear to be lower. This is probably due to hydrothermal activities in the rift zone. The correlation between the heat flow and bathymetric contours is discernable, but with a slight southward shift in the heat flow pattern. Considering the fact that abnormally high and low heat flows are observed near volcanic intrusions, extrusions and faults, and that much higher heat flows would be expected if the full sedimentation effects were eliminated, we suggest that the magma associated with the extension of the southwest ern Okinawa Trough has at least extended into the southwestern end of the Okinawa Trough, in northeast Taiwan.