Heat Flow and Electromagnetic Studies in the Continental Shelf Area off Eastern China

1.我们开展了一项日中合作研究计划，调查中国东部大陆架地区的热结构。1990年和1991年在东海进行了三次研究航行。在东海等浅海区，要确定热流值，必须消除底层水温变化的影响。(1)我们试图使用长探头在同一个站点重复测量沉积物温度剖面，但由于一次事故，无法在一次巡航中进行测量。对另外两个航次的数据进行了分析，假设年度底层水温变化。在最北端的冲绳海槽，热流估计约为90 mW/m^2，而在上海近海，热流低于50 mW/m^2。为了准确测定，需要进行更多的测量。(2)We在海底部署了一个长期温度监测系统来记录海底水温变化，但由于弹出机制存在故障而无法恢复.我们在九州岛外部署了海底电磁仪，以确定电导率结构。虽然仪器不能正常工作，但我们可以获得一些磁场数据，这表明北方冲绳海槽的某些部分具有相对较低的磁电阻率.我们还尝试使用钻孔来确定热流。(l)在东海，我们在钻井完成后的一小时内进行了浅孔温度测量，但记录太短，无法外推到平衡。(2)在南海北方边缘，利用岩心温度测井和热导率资料可以计算深部油气威尔斯井的热流.我们可以找出各种方法在浅海地区的热流测量，这可以在未来的合作研究中解决的问题。

1. We carried out a Japan-China cooperative research program to investigate the thermal structure of the continental shelf area off eastern China. Three research cruises were conducted in the East China Sea in 1990 and 1991.2. The effect of bottom water temperature variation must be removed to determine heat flow in shallow sea areas, such as the East China Sea.(1) We tried to measure sediment temperature profiles repeatedly at the same stations using long probes, but could not make measurements on one cruise due to an accident. The data from the other two cruises were analyzed assuming annual bottom water temperature variation. Heat flow was estimated to be around 90 mW/m^2 in the northernmost Okinawa Trough and lower than 50 mW/m^2 off Shanghai. More measurements are necessary for accurate determination.(2)We deployed a long-term temperature monitoring system on the seafloor to record the bottom water temperature variation, but could not retrieve it due to some fault in the pop-up mechanism.3. We deployed ocean bottom electromagnetometers off Kyushu to determine the electrical conductivity structure. The instruments did not work properly, but we could obtain some magnetic field data, which indicate that some part of the northern Okinawa Trough has relatively low resistivity.4. We also tried to determine heat flow using drill holes.(l) In the East China Sea, we made temperature measurements in shallow holes in one hour after completion of drilling, but the records were too short to be extrapolated to the equilibrium.(2) At the northern margin of the South China Sea, heat flow could be calculated in deep oil/gas wells from temperature logs and thermal conductivity of core samples.5. We could identity problems in various methods for heat flow measurements in shallow sea areas, which can be solved in future cooperative studies.