Groundwater-level Anomalies Associated with a Hypothetical Preslip Prior to the Anticipated Tokai Earthquake: Detectability Using the Groundwater Observation Network of the Geological Survey of Japan, AIST -- Earthquake-related Changes in Groundwater Levels at the Dogo Hot Spring, Japan -- Flow Changes and Geochemical Anomalies in Warm and Cold Springs Associated with the 1992-1994 Seismic Sequence at Pollina, Central Sicily, Italy -- Precursory Subsurface 222Rn and 220Rn Degassing Signatures of the 2004 Seismic Crisis at Tenerife, Canary Islands -- Soil H2 and CO2 Surveys at Several Active Faults in Japan -- Diffuse Emission of Hydrogen from Poás Volcano, Costa Rica, America Central -- Anomalous Emissions of SO2 During the Recent Eruption of Santa Ana Volcano, El Salvador, Central America -- Crater Lake Temperature Changes of the 2005 Eruption of Santa Ana Volcano, El Salvador, Central America -- Temporal Variability of Major and Trace Element Concentrations in the Groundwaters of Mt. Etna (Italy): Effects of Transient Input of Magmatic Fluids Highlighted by Means of Cluster Analysis -- Continuous, Direct Gas-Geochemical Monitoring in Hydrothermal Vents: Installation and Long-Term Operation on Nisyros Island (Greece). Terrestrial fluids, earthquakes and volcanoes: The Hiroshi Wakita Volume II is a special publication to honor Professor Hiroshi Wakita for his scientific contribution to science and commemorate his 10th anniversary as Emeritus Professor at The University of Tokyo. This second special issue of Pure and Applied Geophysics consists of 10 original contributions written by researchers from Japan, Germany, Italy, Costa Rica, Sweden, El Salvador, Turkey, USA, Greece, and Spain. The discussed subjects include research on earthquake-related hydrologic and geochemical observed temporal changes, diffuse degassing in active tectonic and volcanic settings, the observed changes on gas emission and temperature prior volcanic eruptions, magma degassing signature in the groundwater system of active volcanic, and the development of recent technology for continous monitoring of volcanic gases. The Hiroshi Wakita volume II will be useful to students and professional researchers who are interested in the role of terrestrial fluids in earthquakes and volcanic activity.