Monte Vettore fault scarp
Surface displacement on the Monte Vettore Fault from the October 2016 Norcia earthquake.
Earthquake Processes

Research

Current research projects in the Earthquake Processes group look at natural and human induced earthquakes in a variety of fault settings at a range of depths in the crust.

Research in the Earthquake Processes group uses seismic, geological, and geodetic observations coupled with modeling to study how deformation in the crust leads to both slow and fast fault slip. The work in our group is divided into four broad directions:

  • Earthquake interactions: remote dynamic triggering and human induced earthquakes
  • Fault strength studies
  • Fault-fluid interactions
  • Intraplate seismic studies: geodetic and seismic observations

We place an interdisciplinary focus on the study of earthquake and faulting processes, using data-driven approaches to study faults, fault strength, and stress conditions associated with a fault slip over a range of speeds. We use classical ground motion and GPS measurements, time-series processing, poroelastic and viscoelastic modeling approaches, photogrammetry, and geological observations in a number of projects aimed at quantifying earthquake sources. 

The goal of this new initiative in the Earthquake Processes group is to implement Distributed Acoustic Sensing (DAS) in earthquake and faulting process research within our group.  DAS shows great promise to improve the resolution by which we can observe both the fault rupture process, as well as the stress loading in the surrounding medium leading up to an earthquake. The technology belongs to a class of techniques referred to as Distributed Fiber Optic Sensing (DFOS). DFOS techniques make use of existing optical fibers, and turn them into an array of sensors spaced every few meters along cables that cover extended distances on the Earth’s surface. By leveraging existing infrastructure not originally intended for earthquake research, DFOS has the potential to image crustal deformation, including fault slip, as well as off-fault processes, including fluid-rock interactions, at a resolution and spatial scale that will likely remain impossible by standard observatories. The aim is to image the geological structures that were previously inaccessible, and that likely play a key role in fault loading. This work is funded by the Volkswagen Foundation.

DAS wird die Auflösung der Untergrund erhöhen
Gefördert von der VW Stiftung
Induzierte Erdbeben aufgenommen von dem Seismisches Netwerk der RUB, McGill Universität und NRCan
Induzierte Erdbeben Katalog erstellt von Messstationen der RUB (Lehrstuhl Hydrogeomechanik) und der McGill University, in Kollaboration mit Natural Resources Canada

The earth's crust is permeated with faults, both at plate boundaries and in continental interiors. While the movement of tectonic plates is one way to load faults and prime them for slip, other types of stress interactions also load faults. For example, the passing waves of earthquakes can cause transient stress perturbations on neighboring faults at distances ranging from meters to 100s of kilometers. Human activity associated with energy production, such as the injection and/or extraction of fluids or rock materials from the subsurface can also perturb stresses and generate earthquakes. The Earthquake Processes group conducts research related to earthquake nucleation by earthquake-earthquake interactions (triggering) and by anthropogenic stress loading. 

  • Hydraulic fracturing and wastewater disposal induced seismicity in the Western Canada Sedimentary Basin, the Central United States, the Rhein Ruhr region
  • Remotely dynamic triggered earthquakes in western Canada, the lower Rhine Embayment, central Italy, among other regions of study
  • Remote triggering of earthquake and tectonic tremor in the Mediterranean Basin, Greece, and in the North Anatolian Fault zone
Normierte Statisches Stress Drop berechnet für Erdbeben in der Apenninen
Statisches Stress Drop berechnet für Erdbeben der Amatrice-Visso-Norcia Sequenz in zentral Italien (2016)

Seismometers measure ground motion during an earthquake as a function of time, and make recordings called seismograms. Seismograms contain information about properties of an earthquake, such as how large it was, and the difference in stress before and after the earthquake occurred, or static stress drop.  Static stress drop can provide information about how dangerous a given population of earthquakes might be, but it is difficult to measure robustly for the more common, numerous, smaller earthquakes. Part of our work focuses on measuring static stress drop, determining what the observational limitations on stress drop observations are, and most importantly, what the spatial and temporal evolution of stress drop tells us about fault strength.  In particular we measure stress drop in a variety of fault settings, including: 

  • Subduction zone interfaces and in faults in the overriding plate 
  • Interplate faults that are associated with seismic zones or regions of induced seismicity in continental interiors
  • Normal faulting settings and regions of backarc extension

Using strain rates to infer stress loading in intraplate tectonic settings can help quantify where large, infrequent earthquakes can occur. Work led by Dr. Gianina Meneses aims at: 

  •  Estimating a continuous strain rate field and an accurate map of its spatial resolution, including survey local networks and continuous GPS in easter Canada
  • Studying the respective roles of the stress-inducing mechanisms, such as far field tectonic forces, glacial rebound, and structural inheritance, in controlling the seismicity associated in the Western Quebec (WQSZ), Lower St. Lawrence (LSZ), and Charlevoix (CSZ) seismic zones.
  • Quantifying internal deformation and the relation to relocated seismicity to develop a structural stress model for the paleo-rift faults and a meteorite impact zone.  
Interpolierter Strain Rate der Charlevoix Seismischen Zone

Geological fault zones are large discontinuities within a rock volume, which strongly influence fluid pathways. They can determine the success or failure of various projects, including geothermal energy production. In this project we aim to evaluate the reservoir potential of Devonian carbonates in the NRW region, as well as provide a larger scale understanding of how fracture networks effect fluid flow properties in the subsurface. In particular, we: 

  • Combine field structural analysis and fracture and fault characterization using scan lines with 3D digital outcrop models and fracture analysis using drone images
  • Use data from the structural analysis to build a 3D Discrete Fracture Network (DFN) of the fault zone to detect possible permeability anisotropies and optimal conduits for fluid flow 
  • Simulate fluid injection/extraction using realistic hydromechanical properties of the reservoir in a finite element model (Comsol Multiphysics). This will help predicting fluid flow and pressure/stress changes in a potential geothermal reservoir.
Erdbebenprozesse - AV NRW Project
3D model of the Steltenberg quarry wall constructed using 60 drone images and corresponding crustal model

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