Hydraulic fracturing has been and continues to be a major techno­ logical tool in oil and gas recovery, nuclear and other waste disposal, mining and particularly in-situ coal gasification, and, more recently, in geothermal heat recovery, particularly extracting heat from hot dry rock masses. The understanding of the fracture process under the ac­ tion of pressurized fluid at various temperatures is of fundamental scientific importance, which requires an adequate description of thermomechanical properties of subsurface rock, fluid-solid interaction effects, as well as degradation of the host rock due to temperature gradients introduced by heat extraction. Considerable progress has been made over the past several years in laboratory experiments, analytical and numerical modeling, and in-situ field studies in various aspects of hydraulic fracturing and geothermal energy extraction, by researchers in the United States and Japan and also elsewhere. However, the results have been scattered throughout the literature. Therefore, the time seemed ripe for bringing together selected researchers from the two countries, as well as observers from other countries, in order to survey the state of the art, exchange scientific information, and establish closer collaboration for further, better coordinated scientific effort in this important area of research and exploration.

First Japan-United States Joint Seminar on Hydraulic Fracturing and Geothermal Energy, Tokyo, Japan, November 2-5, 1982.- Special Presentations.- Geothermal Energy Development in Japan (General Lecture).- Thermally Induced Cracks and Heat Extraction from Hot Dry Rocks (General Lecture).- Hot Dry Rock Reservoir Development and Testing in the USA.- The Falkenberg Geothermal Frac-Project: Concepts and Experimental Results.- Shallow Depth Experimentation on the Concept of Energy Extraction from Deep Hot Dry Rocks.- Topic 1: Subsurface Structure and Hydraulic Fracturing.- Hydraulic Fracturing Experiment at Nigorikawa and Fracture Mechanics Evaluation.- Breakdown Pressure Prediction in Hydraulic Fracturing at the Nigorikawa Geothermal Field.- The Influence of Subsurface Conditions on Hydraulically Induced Fractures in Deep Rocks.- Evaluation of Artificial Fracture Volume Based on Vented Water at Yakedake Field.- Propagation of Hydraulic Fracture and Its Conductivity in Layered Media.- Hydraulic Fracturing in Geological Processes: A Review.- Topic 2: Rock Mass Properties in the Presence of Pressurized Fluid at Elevated Temperatures.- A Method of Estimating Underground Temperature from a Solution of Iterative Least-Squares Interpretation of Schlumberger's Resistivity Sounding Curves in Geothermal Fields.- Measurements of In-situ Stress, Fracture Distribution, Permeability, and Sonic Velocity.- Measurement of Tectonic Stress by Hydraulic Fracturing in Japan.- Rock Mass Behavior Coupled with Pressurized Water Flowing Through the Fracture.- An Assessment of the Factors Affecting Hydraulic Fracture Containment in Layered Rock: Observations from a Mineback Experiment.- Theory and Application of Hydraulic Fracturing Technology.- Fracture Toughness Evaluation of Rocks in thePresence of Pressurized Water at Elevated Temperature.- Topic 3: Mapping of Subsurface Fractures.- Application of Seismic Inverse Methods to Mapping of Subsurface Fractures.- Detection of the Newly Formed Fracture Zone by the Seismological Method.- Strike-Dip Determination of Fractures in Drillcores from the Otake-Hatchobaru Geothermal Field.- Hydraulic Fracturing and Fracture Mapping at Yakedake Field.- In-situ AE Measurement of Hydraulic Fracturing at Geothermal Fields.- Topic 4: Simulation of Geothermal Reservoirs.- Experimental Studies on Heat Extraction from Fractured Geothermal Reservoirs.- Simulation of Transient Pressure Behavior in a Fractured Geothermal Reservoir.- Influence of Preexisting Discontinuities on the Hydraulic Fracturing Propagation Process.- Geothermal Reservoir Simulation for Water Dominant Fractured Reservoir.- Crack-Like Reservoir in Homogeneous and Inhomogeneous HDR.- Symposium on Fracture Mechanics Approach to Hydraulic Fracturing and Geothermal Energy, Sendai, Japan, November 8-9, 1982.- Applications of Rock Fracture Mechanics.- A Reservoir Created by Injection of Fluid on a Fault for the Extraction of Geothermal Heat.- Application of Laboratory Fracture Mechanics Data to Hydraulic Fracturing Field Tests.- Finite Element Treatment of Singularities for Thermally Induced Crack Growth in HDR.- Growth of Microcracks in Rocks, and Load-Induced Anisotropy.