All truths are easy to understand once they are discovered; the point is to discover them.
– Galileo Galilei –

Friction, fault behavior

Investigators: Ethan Conrad, A new graduate student starting August 2023, Claudio Faccenna, and Nicola Tisato

To better understand tectonic and fault behavior, we study the evolution of static and dynamic friction during rock deformation. Using rotary shear experiments, we study the evolution of fault slip surfaces, the precursory and co-seismic events that resemble natural earthquakes, and the types of materials that can be considered crustal analogs in tectonic sandbox experiments.

Above: Friction experiment with PMMA. Long displacement. Below: Long displacement stick slip experiment with the Energy-Controlled Rotary Shear (ECoR) apparatus

This research topic is supported by the NSF project: Collaborative Research: High-velocity and long displacement stick-slips: Experimental analogs of earthquake rupture and the seismic cycle (#2240417) PI: Tisato, co-PI: Carpenter (OU). 

Selected references:

  • Conrad, E. M.*, Tisato, N., Carpenter, B. M., & Di Toro, G. (2023) Influence of Frictional Melt on the Seismic Cycle: Insights From Experiments on Rock Analog Material. Journal of Geophysical Research: Solid Earth, 128, (19 pages). DOI: 10.1029/2022JB025695
  • Zhao, Q., Glaser, S. D., Tisato, N., & Grasselli, G. (2020) Assessing Energy Budget of Laboratory Fault Slip Using Rotary Shear Experiments and Micro‐Computed Tomography. Geophysical Research Letters, 47, (9 pages). DOI: 10.1029/2019GL084787

Rock-physics to understand subduction zones

Investigators: A new graduate student starting August 2023, and Nicola Tisato (Past Investigators: Caroline Bland)

With this project, we have been studying the influence of rock elastic properties on the Hikurangi margin style of deformation. The North of the Hikurangi margin deforms slowly, often generating slow-slip events, while the South of the Hikurangi margin is locked, setting the conditions triggering a megathrust earthquake.

A) North Island of New Zealand. Position of the samples collected in 2019 and 2022. The symbol color indicates the age of the sample according to the legend. B) Picture, micro-photography, and XRD analysis of sample MT07(Tisato et al., 2023). C) Pictures of many of the samples collected in 2022.

Summary of laboratory measurements: porosity, ultrasonic velocities, and permeability for samples FB12, MO02, and MT07 . Sample FB12 spans a large porosity range as it compacts during a compression test, mimicking the effect of subduction and accretion. Inset: seismic velocity model for the MC10 SHIRE section that agrees with ultrasonic velocities from laboratory measurements (double arrows). A newly proposed porosity-permeability relation (b) fits literature data on mudstone permeability better than a commonly used regression (a).

This research topic is supported by the NSF project: Study of the impact of seamount subduction on the outer wedge of the Hikurangi (# 1949171). PI: Van Avendonk, co-PI: Bangs, Tisato

Selected references:

  • Tisato N., C. D. Bland*, H. Van Avendonk, N. Bangs, O. Alamoudi*, K. Olsen, & Andrew Gase, Permeability and elastic properties of rocks from the northern Hikurangi margin: Implications for slow-slip events. Geophysical Research Letters, (19 pages). [link]

Attenuation of seismic waves

Investigators: A new graduate student starting August 2023, and Nicola Tisato (Past Investigators: Ken Ikeda and Michael McCann)

Attenuation describes the energy that elastic waves lose while traveling in a medium. Extrinsic attenuation is related to the geometrical spreading of the elastic energy carried by the wave, while intrinsic attenuation refers to the ability of specific mechanisms to convert the elastic energy of a wave into heat. The conditions at depth, such as the presence of fluids or the temperature, control these mechanisms. Thus measuring seismic wave attenuation and understanding the mechanisms provide insight into the subsurface. The main controls on the intrinsic attenuation in partially saturated rocks are Wave-Induced Fluid Flow (WIFF) and Wave-Induced-Gas-Exsolution-Dissolution (DOI: 10.3389/feart.2021.641177, DOI: 10.1002/2015GL063538). An interesting application is to study attenuation in magmatic chambers to understand when bubbles develop before an eruption (DOI: 10.1029/2020GL092315). We have developed a state-of-the-art attenuation apparatus, the Low-Frequency Module (LFM). LFM takes advantage of the sub-resonance technique to measure the frequency-dependent attenuation of rocks between 0.1 and 100 Hz (thesis).

Another interesting topic is the attenuation of seismic waves in fluids. We study the rheology of multiphase fluids, such as liquids with bubbles and viscous liquids. Bubbly fluids could be present in the subsurface due to hydrothermal processes, carbon-capture-sequestration, and hydrocarbon extraction (thesis). Viscous liquids such as water and guar can be used as proxies for magma and mud.


Ken Ikeda shows low-frequency force oscillation signals (nanometric vertical deformations) to estimate seismic wave attenuation in rocks.

This research topic has been supported by the Edger forum (UT-private companies consortium).

Selected references:

  • Tisato, N., Madonna, C., & Saenger, E. H. (2021) Attenuation of Seismic Waves in Partially Saturated Berea Sandstone as a Function of Frequency and Confining Pressure. Frontiers in Earth Science, 9, (17 pages). DOI: 10.3389/feart.2021.641177
  • Pistone, M., Fife, J. L., Tisato, N., Caricchi, L., Reusser, E., Ulmer, P., Mader K., & Marone F. (2021) Seismic Attenuation During Magma Vesiculation: A Combination of Laboratory Constraints and Modeling. Geophysical Research Letters, 48, (10 pages). DOI: 10.1029/2020GL092315

Combining rock-physics and micro-CT analyses (Digital Rock Physics)

Investigators: Omar Alamoudi and Nicola Tisato (Past Investigators: Eric Goldfarb, Ken Ikeda)

We conduct experimental investigations combining tri-axial testing, micro-CT imaging, and ultrasonic velocities/acoustic emissions, and hydraulic permeability measurements. We use such a combination of methods to better understand the dependence of hydraulic permeability on varying stress, strain, and strain-rate on low-permeability sedimentary rocks such as shales and tight carbonates.

Understanding the mechanical behavior of rocks and their saturating fluid is critical to many geological and engineering fields. It is crucial to optimizing hydrocarbon exploration and development operations, CO2 storage and sequestration, improving geothermal energy yields, and understanding natural and human-made phenomena. Of particular importance is understanding the behavior of fractured geological materials, and the effect of stress on their hydraulic permeability. We reproduce overburden pressure and temperature conditions on rock samples by means of sealed tri-axial testing apparatus, leaving uncertainty on the sample mechanical behavior during the experiment. With the advent of micro-CT imaging, geologists and engineers can reduce such uncertainty by ‘visually’ inspecting the samples during tri-axial testing utilizing micro-CT imaging. Also, advanced micro-CT data analysis allows for the extraction of quantitative information about the rock sample during deformation.

Designing new methods to improve estimates of rock physical properties (e.g., density, porosity, and elastic properties) from analytical methods (e.g., micro-computed tomography: micro-CT). Read more…

Omar Alamoudi mounting the X-Ray Transparent Pressure Vessel (X-RETTA) inside the X-ray scanner. The inset shows the sample assembly inside the X-RETTA.

MicroCT slice of a 3D scan showing how fractures close and permeability changes as a function of confining pressure. The rock is a mudstone collected along the Hikurangi margin in New Zealand.

MicroCT Image Scaling

MicroCT Image Scaling

Simulation of ultrasonic wave propagation in Berea sandstone.

This research topic has been supported by Saudi Aramco, SNSF, DOE project: A multi-scale experimental investigation of flow properties in coarse-grained hydrate reservoirs during production. PI: Flemings, co-PIs: Daigle, Di Carlo, Espinoza, Phillips, Lin, Tisato, Zachary.

Selected references:

  • Ikeda, K., Goldfarb, E. J., & Tisato, N. (2020). Calculating Effective Elastic Properties of Berea Sandstone Using the Segmentation‐Less Method Without Targets. Journal of Geophysical Research: Solid Earth, 125(6).
  • Chen, X., Espinoza, D. N., Luo, J. S., Tisato, N., & Flemings, P. B. (2020). Pore-scale evidence of ion exclusion during methane hydrate growth and evolution of hydrate pore-habit in sandy sediments. Marine and Petroleum Geology, 117, 104340.
  • Ikeda, K.*, Subramaniyan, S., Quintal, B., Goldfarb, E. J.*, Saenger, E. H., & Tisato, N. (2021) Low-Frequency Elastic Properties of a Polymineralic Carbonate: Laboratory Measurement and Digital Rock Physics. Frontiers in Earth Science, 9, (15 pages). DOI: 10.3389/feart.2021.628544
  • Goldfarb, E. J.*, Ikeda, K.*, Ketcham, R. A., Prodanović, M., & Tisato, N. (2022) Predictive digital rock physics without segmentation. Computers & Geosciences, 159, (12 pages). DOI: 10.1016/j.cageo.2021.105008
  • Tisato N., K. T. Spikes, N. Saxena, & R. Hofmann, Scattering and Frequency Effects of Ultrasonic Velocities on Carbonates. Journal of Geophysical Research – Solid Earth, (39 pages). [link]

The genesis of cave deposits

Investigators: Carole Lakrout and Nicola Tisato
We study biologically mediated speleothems, in other words: how microbial life impacts carbonate structures in caves. We use CT and SEM imaging to search for evidence of life on the speleothems. Understanding how life can impact speleothem structures represents a springboard for looking for life in the geological rock record, the study of unconventional energy sources of the extremophiles living on our and potentially on other planets.

Helictites from Breezeway cave at different scales (Colorado -US). In the center and right image, the layer covering the calcite crystals is associated with the remnant of life activity.

  • C.A. Lakrout, E.J. Goldfarb, T.R.R. Bontognali, and N. Tisato, Biotic influence in speleothems morphology, 3rd International Planetary Caves Conference scheduled for February 18–21, 2020 at Southwest Research Institute (SwRI), San Antonio (TX),
  • Lakrout C. A.*, Jones N. T, Tisato N. (2022) Relating Unique Cave Structures to Micro-Biomes, LPI Contributions 2678, 2591, Houston, TX.

Development of an inexpensive seismometer for anthropogenic noise monitoring and outreach

Investigators: Looking for an undergrad student, Thorsten Becker, and Nicola Tisato (Past Investigators: Mason Currin)

We study the seismic waves generated by natural and anthropogenic events such as Longhorns football games (Hook’em!). We use a 3C 40 s, and a vertical 10 Hz, geophone-based seismometer. The latter is called BerryQuake and has been developed as an open-source design among the RDL. The collected data spans several months and includes 2019 season Longhorns football games, allowing us to compare crowd behavior during games and low noise periods, for example, during nights. Future studies might include deploying additional sensors to get a clearer picture of wave propagation from events.