On Causes of Tectonic Earthquakes with External and/or Internal Loadings
Zhong-qi Quentin Yue (The University of Hong Kong)
Prager Medal Symposium in honor of George Weng: Micromechanics, Composites and Multifunctional Materials
Tue 4:20 - 5:40
MacMillan 117
The conventional elastic rebound hypothesis for cause of earthquakes states that tectonic earthquakes are caused by sudden fracture of a brittle rock of the Earth’s crust when the applied stress exceeds its tensile and/or shear strength. The loading system is an external loading at its far field. The released earthquake energy is the stress-strain energy accumulated and stored in the plate rocks which are subjected to the external loading (i.e., the relative movements of plates). The author has proposed a gas hypothesis for the cause of tectonic earthquakes. It states that an earthquake is an adiabatic process of the interaction between the rapid expansion and migration of compressed natural gas mass and its country rocks and soils. So, the loading system is an internal loading in the interior of the two contact fault rocks. The released earthquake energy is the volumetric expansion energy of the dense natural gas. The volume and pressure of the dense natural gas escaped from the traps control the earthquake magnitude. This paper examines the two stress and strain fields in an elastic fault rock system due to either an external loading or an internal loading. The tensile, shear and/or fracture toughness criteria are used to examine the external and internal loadings required for occurring of sudden brittle failure. Under this condition, the stress and strain fields and the elastic stress-strain energies associated with the two systems are examined and compared. The amount of total elastic energy in the external loading system is far greater than that in the internal loading system. The stress magnitudes in the external loading system are also far larger than those in the internal loading system. The results can demonstrate that the internal gas loading can be much easier to cause the sudden rupture isolated in crustal rocks than the external plate loading. The comparison gives a theoretical base for the cause of earthquakes by internal loading of compressed gas.