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.