Nicola Tisato

Nicola Tisato
University of Texas at Austin | UT · Department of Geological Sciences

PhD
Trying to make sense between viscosity and attenuation of seismic waves...

About

106
Publications
21,752
Reads
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1,288
Citations
Introduction
To grasp what I do you could watch this: https://mediasite.jsg.utexas.edu/UTMediasite/Play/c2104c99592247a690fa535d5235e5f01d. My research focuses on the determination of rock elasticity and low-frequency seismic wave attenuation, fluid pressure transients generated by stresses. I am also interested in DRP: http://www.jsg.utexas.edu/news/2020/06/jackson-school-team-builds-better-rock-models/, friction coefficient during seismic slip, and the genesis of caves and speleothems.
Additional affiliations
January 2016 - present
University of Texas at Austin
Position
  • Professor (Assistant)
January 2016 - July 2016
University of Texas at Austin
Position
  • Professor (Assistant)
January 2014 - December 2015
University of Toronto
Position
  • PostDoc Position
Description
  • Position granted by SNSF

Publications

Publications (106)
Article
Measuring physical properties from rock samples is necessary in geosciences to calibrate models from geophysical surveys. Digital rock physics is one way to estimate these properties. X-ray computed tomography (CT) images can be used to create 3D numerical models of rocks. Numerical simulations on such models are proxies for tests performed in the...
Article
Full-text available
Frequency-dependent attenuation (1/Q) should be used as a seismic attribute to improve the accuracy of seismic methods and imaging of the subsurface. In rocks, 1/Q is highly sensitive to the presence of saturating fluids. Thus, 1/Q could be crucial to monitor volcanic and hydrothermal domains and to explore hydrocarbon and water reservoirs. The exp...
Article
Full-text available
Assessing the potential and likelihood of explosive eruptions is vital for almost 800 million people living near active volcanoes. Magma reservoirs are not directly accessible, limiting our capability to understand the prerequisites for an explosive eruption and our ability to perform experiments that simulate magmatic processes at depth. Therefore...
Article
Full-text available
We demonstrate that the static elastic properties of a carbonate sample, comprised of dolomite and calcite, could be accurately predicted by Digital Rock Physics (DRP), a non-invasive testing method for simulating laboratory measurements. We present a state-of-the-art algorithm that uses X-ray Computed Tomography (CT) imagery to compute the elastic...
Article
Full-text available
We propose a new method to compute elastic properties of rocks from computed tomography (CT) images. A CT volume captures X‐ray attenuation, which is scaled in a CT number unit. Our method improves an existing segmentation‐less method where the CT volume is directly converted to elastic property arrays without using segmentation. A drawback of the...
Article
Hydrate-bearing sediments constitute complex hydrological systems, within which the pore habit of hydrate significantly affects all physical properties. However, there is scarce pore-scale evidence of the evolution of hydrate growth in porous media and the influence of water salinity in the micro-morphology of hydrate. In this paper, we used X-ray...
Article
Full-text available
Quantitative assessment of the energy budget of earthquake events is one of the key aspects for understanding the physics of earthquakes. Investigation of laboratory fault slips under controlled conditions can provide insights on this important aspect of the natural and induced earthquakes. We conducted a rotary shear experiment under X‐ray micro‐c...
Article
Shales commonly exhibit anisotropy in their elastic wave velocity, which directly impacts the accuracy of seismic imaging and their geomechanical response to drilling and completions. Anisotropy is often caused by mineralogical layering, fractures and rock fabric (i.e. oriented grains and intrinsic anisotropy of clay sediments). However, the relati...
Article
Full-text available
Several theoretical studies indicate that a substantial fraction of the measured seismic anisotropy could be interpreted as extrinsic anisotropy associated with compositional layering in rocks, reducing the significance of strain-induced intrinsic anisotropy. Here we quantify the potential contribution of grain-scale and rock-scale compositional an...
Article
The rapid and nonintrusive deployment of seismic sensors for near-surface geophysical surveys is of interest to make data acquisition efficient and to operate in a wide variety of environmental and surface-terrain conditions. We have developed and compared near-surface data acquired using a traditional vertical geophone array with data acquired usi...
Conference Paper
Full-text available
The study of wave-induced-fluid-flow is fundamental to understand attenuation of seismic waves in saturated rocks. In the laboratory, one way to better understand wave-induced-fluid-flow in saturated rocks is to measure how pore pressure evolves during wave propagation. Here, we show and discuss the results of a laboratory experiment in which we me...
Poster
Full-text available
Digital Rock Physics (DRP) has become an avenue to investigate effective-properties of geomaterials. Micro-computed tomography (μCT) and segmentation methods provide digital models. But, segmentation proves to be a challenging and arbitrary procedure that typically lead to inaccurate estimates of physical properties. Here we propose a new technique...
Article
A flight of marine terraces along the Cuban coast records Quaternary sea‐level highstands and a general slowly uplifting trend during the Pleistocene. U/Th dating of these limestone terraces is difficult because fossil reef corals have been affected by open system conditions. Terrace ages are thus often based on geological and geomorphological obse...
Article
Full-text available
Friction and fault surface evolution are critical aspects in earthquake studies. We present the preliminary result from a novel experimental approach that combines rotary shear testing with X-ray micro-computed tomography (${\mu}$CT) technology. An artificial fault was sheared at small incremental rotational steps under the normal stress of 2.5 MPa...
Article
Full-text available
Despite their importance for eruption forecasting the causes of seismic rupture processes during caldera unrest are still poorly reconstructed from seismic images. Seismic source locations and waveform attenuation analyses of earthquakes in the Campi Flegrei area (Southern Italy) during the 1983–1984 unrest have revealed a 4–4.5 km deep NW-SE strik...
Conference Paper
We use Biot’s quasi-static equations to numerically simulate oscillatory compression tests on 3D models representative of laboratory samples. Simulations are performed on cylindrical models that have equally a total 99% water saturation but distinct fluid distributions; their curved boundaries are either open (drained) or closed (undrained). For un...
Article
Earthquake-triggered volcanic activity promoted by dynamic and static stresses are considered rare and difficult-to-capture geological processes. Calderas are ideal natural laboratories to investigate earthquake–volcano interactions due to their sensitivity to incoming seismic energy. The Campi Flegrei caldera, Italy, is one of the most monitored v...
Article
A rotary shear apparatus (ERDµ-T) was designed, assembled and calibrated to study frictional behavior. We paired the apparatus with X-ray micro-computed tomography (µCT) to inspect in-situ and in-operando deformation of the tested specimen. This technology allows us to observe how two rough surfaces interact and deform without perturbing the experi...
Article
Full-text available
Seismic wave attenuation is frequency dependent in rocks saturated by two fluid phases and the corresponding scaling behaviour is controlled primarily by the spatial fluid distribution. We experimentally investigate the frequency scaling of seismic attenuation in Berea sandstone saturated with two fluid phases: a liquid phase, water, and a gas phas...
Article
Full-text available
Many morphological elements in Cuba's landscape (e.g., marine terraces, tidal notches) demonstrate that coastal uplift has taken place, but the rate at which this occurs is not known. Carbonate phreatic overgrowths on speleothems have been found in a cave in Central North Cuba, ~1 km from the present coastline at 16 m asl. They form exceptional and...
Conference Paper
Geophysical methods rely on the accurate determination of physical and mechanical properties of rocks. These properties are intimately related to rock microscopic features such as pore shape and distribution, grain orientations, and fluid distribution. The present contribution reports the preliminary results obtained with a newly conceived high pre...
Conference Paper
Full-text available
In the last few years, Digital Rock Physics (DRP) has become an avenue to investigate effective properties of geomaterials. In particular, the physical properties of samples imaged using micro-computed tomography (μCT) are estimated through segmentation of the μCT dataset. Nevertheless, segmentation proves to be a challenging and arbitrary procedur...
Article
Full-text available
Seismic attenuation and velocity dispersion are potentially able to reveal the rock physical properties of the subsurface. Conventionally, a frequency-independent quality factor (Q) is measured. This Q is equivalent to the total velocity dispersion in a seismic record and is inadequate for analysing the attenuation mechanism or rock physical proper...
Article
Full-text available
UnusualspeleothemsresemblinggiantmushroomsoccurinCuevaGrandedeSantaCatalina,Cuba.Althoughthesemineralbuildupsareconsideredanaturalheritage,theircompositionandformationmechanismremainpoorlyunderstood.Herewecharacterizetheirmorphologyandmineralogyandpresentamodelfortheirgenesis.Weproposethatthemushrooms,whicharemainlycomprisedofcalciteandaragonite,fo...
Article
Full-text available
Deep geological repositories, isolated from the geosphere by an engineered bentonite barrier, are currently considered the safest solution for high-level radioactive waste (HLRW) disposal. As the physical conditions and properties of the bentonite barrier are anticipated to change with time, seismic tomography was suggested as a viable technique to...
Poster
Full-text available
The study of acoustic emissions (AE) generated by rocks undergoing deformation has become, in the last decades, one of the most powerful tools for boosting our understanding of the mechanisms which are responsible for rock failures. AE are elastic waves emitted by the local failure of micro- or milli-metric portions of the tested specimen. At the s...
Article
Full-text available
Using the forced oscillation method, we measure the extensional-mode attenuation and Young's modulus of a Berea sandstone sample at seismic frequencies (0.5-50 Hz) for varying levels of water saturation (~0-100%) and confining pressures (2-25 MPa). Attenuation is negligible for dry conditions and saturation levels <80%. For saturation levels betwee...
Article
Full-text available
Active and passive ultrasonic methods were used to study the evolution of attenuation properties in a sample of Fontainebleau sandstone during true-triaxial deformation. A cubic sample of Fontainebleau sandstone (80 mm $$\times$$× 80 mm $$\times$$× 80 mm) was deformed under true-triaxial stresses until failure. From the stress state: $$\sigma _3 =...
Article
Full-text available
The study of acoustic emissions (AEs) is of paramount importance to understand rock deformation processes. AE recorded during laboratory experiments mimics, in a controlled geometry and environment, natural and induced seismicity. However, these experiments are destructive, time consuming and require a significant amount of resources. Lately, signi...
Article
Full-text available
OPEN ACCESS ARTICLE AT: http://www.nature.com/articles/srep15525 Helictites—an enigmatic type of mineral structure occurring in some caves—differ from classical speleothems as they develop with orientations that defy gravity. While theories for helictite formation have been forwarded, their genesis remains equivocal. Here, we show that a remarkable...
Conference Paper
Full-text available
Seismic wave attenuation (1/Q) is a physical property that might be considered in seismic tomography to improve the subsurface imaging. In particular, it may help in the exploration of unconventional reservoirs as these resources are hosted in highly attenuating geo-materials. One of the factors increasing visco-elasticity of rocks (i.e. 1/Q) is th...
Article
Folia are an unusual speleothem type resembling inverted cups or bracket fungi. The mechanism of folia formation is not fully understood and is the subject of an ongoing debate. This study focuses on an occurrence of folia present in Santa Catalina Cave, a non-thermal epigenic cave located close to Matanzas (Cuba). The sedimentology, morphology, pe...
Conference Paper
Full-text available
While the shear behaviour of rock mass discontinuities has been extensively studied in the past, uncertainties regarding the mechanisms by which surface asperities deform and degrade under shear and how this degradation influences the aperture distribution remains. Although studies have attempted to investigate asperity failure mechanisms, they hav...
Conference Paper
Laboratory measurements of seismic attenuation were performed on a synthetic rock sample using the forced oscillation method. Studying first the effect of partial water saturation, significant and frequency-dependent attenuation was only observed at near full water saturation and at low pore fluid pressures (≤0.6 MPa). Increasing the confining pres...
Research
Full-text available
Physical and mechanical properties of rocks are essential information for geophysical methods. However, these properties are intimately related to microscopic features such as pore shape and distribution, grain orientation, saturation and fluid distribution. Therefore, to fully and deeply comprehend macroscopic rock properties there is a quest to u...
Article
The migration of gases from deep to shallow reservoirs can cause damageable events. For instance, some gases can pollute the biosphere or trigger explosions and eruptions. Seismic tomography may be employed to map the accumulation of subsurface bubble-bearing fluids to help mitigating such hazards. Nevertheless, how gas bubbles modify seismic waves...
Conference Paper
Full-text available
During the expedition organized by La Salle 3D – International Team, Photo, Video and Documentation in December 2012 several caves close to Matanzas, on the northern coast of Cuba 90 km E of Havana, have been investigated. In particular the Cueva de Santa Catalina hosts a wide variety of speleothems among which the common stalactites, stalagmites,...
Article
Full-text available
The risks and uncertainties related to the storage of high-level radioactive waste (HLRW) can be reduced thanks to focused studies and investigations. HLRWs are going to be placed in deep geological repositories, enveloped in an engineered bentonite barrier, whose physical conditions are subjected to change throughout the lifespan of the infrastruc...
Conference Paper
Full-text available
Seismic wave attenuation (1/Q) is an important parameter which could potentially be used to improve geophysical prospection. In partially water-saturated Berea Sandstone, attenuation can be caused by wave induced fluid flow (WIFF) at frequencies >10 Hz. A series of sub-resonance experiments, obtained with the Broad Band Attenuation Vessel and a Ber...
Article
Full-text available
In the past few decades, great attention has been focused on uncovering the physics of seismic wave attenuation in fluid-saturated rocks. However, the relationship among many variables affecting attenuation is still not completely clear. For instance, although the role of strain in enhancing friction dissipation is relatively well known for dry roc...
Article
Full-text available
Intrinsic wave attenuation at seismic frequencies is strongly dependent on rock permeability, fluid properties, and saturation. However, in order to use attenuation as an attribute to extract information on rock/fluid properties from seismic data, experimental studies on attenuation are necessary for a better understanding of physical mechanisms th...
Article
Gypsum (CaSO4 center dot 2H(2)O), alunite (KAl3(SO4)(2)(OH)(6)), and rare phosphate-sulphate sanjuanite Al-2(PO4)(SO4)(OH)(9)(H2O) and rossiantonite (Al-3(PO4)(SO4) 2(OH)(2)(H2O)(14)) have recently been identified as secondary mineral deposits in different quartz-sandstone caves in the Gran Sabana region, Venezuela. Due to the extended time scale r...
Article
Full-text available
The large amount of data collected with the broadband attenuation vessel (BBAV) and other laboratory devices and analyzed in the last five years sheds light on the physics of wave-induced fluid flow in Berea Sandstone. However, the knowledge is insufficient to fully exploit the physics of seismic wave attenuation in partially saturated rocks. In pa...