things happen before earthquakes

I read an interesting paper from J. Byerlee on "Model for episodic flow of high-pressure water in fault zones before earthquakes".

This is a part of a dialog between authors on the role of high-pressure water in the fault zones: where the water come from and how it effects fault zones. The flow of high-pressure water differs in their temporal behaviors: no flow, continuos flow and episodic flow. Although this paper is written in 1993, things haven't been clearer since then. Perhaps the discovery of tremor and related phenomena make things more difficult to explain.

Here is today's theme: Things happened before earthquakes. It is an interesting theory. The following story is my own interpretation of the paper and one should trace back to the original paper if interested.

Step 1: Water saturated the fault zone. Water can penetrate into crust down to depth of 20 km. The crust is largely in hydrostatic pressure. The fault zone which consists of fine crushed rocks is highly porous and permeable.

Step 2: Compaction of the fault zone at high pressure and temperature. Silica deposits during the compaction and over-saturated water flow out of the fault zone into country rocks. Seals formed after silica deposition.

Step 3: Seals formed compartments. The seal is impermeable. The 3D compartments developed from deep section of the fault zone and propagated upward. The depth distribution of compartments is from 15 km to 3 km depth.

Step 4: Trigger earthquakes. Within the country rock, in order to prevent hydrofracture, the minimum principle stress has to be greater than the pore pressure. But inside the fault zone, the formation of seal allows a smaller minimum principle stress. The pore pressure can be 85% of lithostatic and the minimum principle stress can be only 60%. Before the formation of seal, however, the minimum principle stress has to increase. This is a key point that has been stated a couple of times in the paper, without any explanations. The seal can still break when further pressed, then the water will flow into country rock from the sealed pores, the effective normal stress would increase and the fault will be further locked. When the shear stress is big enough the lithified seal between compartments will be fail, and there will be a increase in the pore pressure and the fault unclamped. Earthquake (or tremor?) will happen as a result of pore pressure change in the fault zone.

Step 5: The earthquake fractures the fault zone, and everything restart.

To me, this is quite an imagination.