Journal Article

Short‐Lived and Voluminous Fluid‐Flow in a Single Fracture Related to Seismic Events in the Middle Crust

Uno, M., Mindaleva, D., Tsuchiya, N.

2023

Overview

This study focuses on samples that underwent rapid hydration (∼10 hr) and evolved in permeability (∼10−9 to 10−8 m2) as a result of crustal fracturing. A coupled reactive transport model and thermodynamic analyses, focusing on Si alteration processes within reaction zones, are used to estimate the fluid volume required to induce fluid‐driven seismic activity. Estimated fluid volumes (101–104 m3) are used to approximate the moment magnitudes of potential seismic events. The resulting moment magnitudes (−0.6 to 3.8) and short timescales of fluid infiltration (∼10 hr) are comparable to some slow‐slip events, such as tremors and low‐frequency earthquakes. This indicates that the voluminous fluid flow in a single fracture could be a key control on the generation of crustal fracturing and the induction of seismic activity above the tremor and slow slip events source regions in the lower–middle crust. Plain Language Summary Short‐lived fluid flow in the crust modifies the hydrological properties of rocks and controls the earthquakes triggering. However, there are limited numerical constraints on the fluid volumes that can be rapidly transported. This study focuses on fluid flow through a single fracture in metamorphic rocks. We discuss the relationship between estimated fluid volumes and a series of low‐magnitude fracturing events, such as tremors and other types of slow slip events in the lower‐middle crust. Specifically, we analyze unique geological and geochemical evidence preserved in fluid‐rock reaction zones to approximate the duration of fluid infiltration and the volume of fluids transported. We use two independent methods for constraining generated seismic moment and magnitude based on fluid volumes and single fracture geometry. The transportation of fluid volumes through a fracture (101–104 m3) may be related to short seismic events, as suggested by duration (∼10 hr) and cumulative magnitude, representing the maximum values as 2.0–3.8. We observed a dramatic change in hydrological properties: from low permeable rocks to high‐permeable fractures, which are not dead‐end and can effectively transport a large volume of fluids in a short time. Such fluid infiltration can possibly trigger seismic activity above the earthquake source regions. Key Points Fluid volumes estimated via reactive‐transport modeling and thermodynamic analyses are used to approximate the moment magnitudes Moment magnitudes (−0.6 to 3.8) and short timescales of fluid infiltration (∼10 hr) are comparable to slow‐slip events Voluminous fluid flow in a single fracture may be related to the generation of crustal fracturing and the induction of short seismic events

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Crustal fractures / crustal fracturing / Earthquakes / Fluid flow / Fluid infiltration / fluid‐rock reaction zone / Fracturing / Open systems / Permeability / Seismic activity / short‐lived fluid flow / Tremors / voluminous fluid flow