Terrestrial heat flow is the sum of the radioactive heat generated in the crust and the heat flow from the mantle. If we can evaluate the radioactive heat generation in the crust more precisely, we can better estimate the heat flow from the mantle and the thermal state in the earth crust. In this study, the authors measured the contents of radioactive elements in rocks of Kohistan volcanic arc, Pakistan and Ichinomegata, northeast Japan. We conclude that low density rocks (ρ_??_2.9) systematically contain much more radioactive elements leading to high heat generation compared with high density rocks (ρ_??_3.0). In the next step, the vertical distribution of radioactive heat generation in the crust was estimated, and the heat generation of the lower crust in the two areas was found to be much lower than previously considered. It means, if the surface heat flow is the same, the estimated temperature at 30km depth is about 80°C higher than previous estimates. This temperature change may strongly affect the seismic activity at the depth
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