We report 30 new conductive heat flow measurements collected on the Juan de Fuca plate, offshore of Grays Harbor, Washington, just seaward of the deformation front. The data were collected along Cascadia Open‐Access Seismic Transect Lines 4 and 5. A prominent basement high associated with a rift propagation pseudofault is imaged near the western end of Line 4. Lithospheric conductive cooling models, for 9 Ma oceanic crust, predict that heat flow should be ~175 mW m⁻². Just seaward of the deformation front heat flow values corrected for the impact of sedimentation are ~200 mW m⁻² and rapidly rise to a value of ~750 mW m⁻² over the basement high. We find that (1) hydrothermal circulation redistributes heat in the Juan de Fuca plate offshore Grays Harbor, (2) heat in addition to the basal heat flux is required to fit the data, and (3) this heat likely results from a combination of fluid flow associated from ongoing hydrothermal circulation within the subducted oceanic crust and possibly with the pseudofault. Our data and modeling support previous inferences that hydrothermal circulation within the subducting oceanic crust plays an important control on plate interface temperatures.

中文翻译：

---

华盛顿洋灰海岸近海灰壳热液循环热流证据

我们报告了30个新的传导热流测量值，这些测量值是从华盛顿州格雷斯港（Grays Harbor）海上的胡安·德·富卡（Juan de Fuca）平板上向变形前沿靠海处采集的。数据是沿着4号和5号卡斯卡迪亚开放存取地震剖面线收集的。在4号线的西端附近，一个与裂谷传播伪断层有关的显着基底高被成像。对于9 Ma大洋壳，岩石圈传导冷却模型预测了热量流量应为〜175 mW m ^-2。刚经过变形的海面，针对沉积影响校正的前热流值为〜200 mW m ^-2，并迅速上升到〜750 mW m ^-2在地下室高处。我们发现（1）水热循环重新分配了格雷斯港（Grays Harbor）沿胡安德富卡板块的热量，（2）除基础热通量外还需要热量来拟合数据，（3）这种热量可能是由于与俯冲洋壳内部正在进行的热液循环有关的流体流动，并可能与假断层有关。我们的数据和模型支持以前的推断，即俯冲洋壳内的热液循环对板界面温度起重要控制作用。