It has been documented for many centuries that earthquakes and other tectonic processes have hydrological effects.  The magnitude and the spatial and temporal patterns of such signals recorded by scientific instruments in modern times have not always been straightforward to explain, and hence remain the subject of active research, especially those that might be precursors to earthquakes. This volume contains 9 papers that present new observations on earthquake-related hydrological, geochemical, and geophysical changes in Japan, Taiwan, Baja California in Mexico, and mostly China, one paper on laboratory rock-mechanics study, and a brief overview of Chinese research on earthquake prediction during the past 5 decades.  Some of the observed changes occurred several days before earthquakes, and are explained with the consideration of heterogeneity of the earth's crust and earthquake-related slow-slip events, with earthquake forecasting as a possible application.