Rock Physics Laboratories
There are currently two main Experimental Rock Physics Laboratories in the Earthquake Science Center in Menlo Park, California. These laboratories specialize in generating earthquakes under controlled conditions.
Rock Physics Labs
There are currently two main Experimental Rock Physics Laboratories in the Earthquake Science Center in Menlo Park, California. These laboratories specialize in generating earthquakes under controlled conditions to measure the processes that determine how they start and how large they will become. Since most damaging earthquakes originate many miles below the earth’s surface, it is almost impossible to study them directly. Instead, much of what we know about natural earthquakes comes from analyzing the seismic waves that they produce.
In the laboratory, however, we are able to recreate the conditions of high pressure, high temperature and slow stress buildup that faults undergo in the months to years before earthquakes. We also have specialized testing machines that slide rocks against each other at the high speeds (meters per second) that occur during earthquakes. Because testing is carried out in a controlled environment, relevant properties are measured before, during and after the occurrence of laboratory earthquakes. These include strength and frictional behavior of rocks and fault zone materials, the velocity of seismic waves through rock, electrical resistivity measurements, as well as the role of fluids and fluid flow in fault zones.
How is this Data Used?
Information on rock properties is combined with other geophysical observations to improve our models of the earthquake process, such as the timing and magnitude of earthquakes, earthquake triggering, recurrence, rupture propagation, and ground motion. This in turn is necessary to understand earthquake hazards and risk in earthquake-prone areas.
Why study the friction of rock? - A Primer on Laboratory Friction Studies
Why study the friction of rocks? Most earthquakes are caused by sudden movement on preexisting faults. An understanding of the frictional forces between rock surfaces is important for understanding earthquake behavior. A simple analogy would be a block and spring experiment: A block rests on a flat surface, and a force is applied to it by pulling the end of the attached spring slowly. The block can respond in different ways. In one scenario, the block may slide forward smoothly, with a constant force in the spring. This stable sliding of the block is equivalent to creep along an active fault. Alternatively, a force is applied to the block by the spring, and at first the block does not move. The spring keeps pulling until suddenly, the block slips forward and the force in the spring drops. The cycle begins again with the force applied by the spring increasing until the block suddenly slips again. This is called stick-slip behavior. Many phenomena are caused by stick-slip behavior, such as the music produced by bowed instruments, the noise of car brakes and even the sound from grasshoppers. In rock friction experiments, stick-slip behavior is the laboratory equivalent of the earthquake process.
Both types of deformation can occur in the block and spring model depending on characteristics of the sliding surface and the spring. Likewise, both types of deformation occur along faults such as the San Andreas in California. The northern and southern portions of the San Andreas Fault are locked for long periods of time as stresses build up in the earth due to the relative motion of the Pacific and North American Plates. When the fault can no longer support the increasing stress, it suddenly slips, releasing stored up energy and causing an earthquake. In Central California, however, the San Andreas Fault slowly creeps, causing numerous microearthquakes but no large events.
The simple block and spring model is not adequate to simulate the complexities of fault behavior at depth in the earth, so several types of experimental apparatus have been devised for more realistic laboratory experiments.
In a biaxial experiment, a test geometry in which forces are applied in two directions, rectangular blocks of rock are squeezed together, and at the same time made to slide past one another due to an applied vertical force. Displacement of the blocks and the force necessary to cause slip between the blocks are recorded. From this, the frictional shear strength of the fault surfaces can be determined. This is commonly described by the coefficient of friction of the rock, µ, defined as the ratio of shear stress, τ, (the stress in the direction of sliding) to normal stress, σn, (the stress pushing the blocks together) and is an important physical parameter used in the modeling of earthquake behavior.
In a triaxial experiment in which forces are applied to the sample in all directions, a cylindrical sample of rock is sealed in a leak-proof jacket and then placed inside a pressure vessel. The vessel is pressurized to simulate the forces acting on all sides of the rock at depth in the earth. The rock can then be further squeezed along its vertical axis with a piston, simulating the additional tectonic forces in the earth. In a triaxial apparatus, the failure strength of intact rock (force required to break the specimen) can be determined, as well as the frictional strength (force required to slide on preexisting fractures).
The total amount of slip between rock surfaces in both biaxial and triaxial experiments is limited by the geometry of the apparatus. When greater fault displacements are desired, a third type of apparatus called a rotary shear machine is used. In this type of experiment, two rings of rock rotate past one another so that the relative displacement on the simulated fault surface can be very large. Also, this apparatus can be operated at high slip rates, simulating the actual rupture speed during an earthquake.
Other important parameters that affect the behavior of faults in the earth are pore fluid pressure and temperature. These conditions are both reproduced in laboratory triaxial experiments by injecting water into the rock and heating the sample during testing. In this way, all of the important conditions controlling earthquakes on natural faults are reproduced on test specimens in the laboratory.
Related Content
KG²B, a collaborative benchmarking exercise for estimating the permeability of the Grimsel granodiorite - Part 1: measurements, pressure dependence and pore-fluid effects
KG²B, a collaborative benchmarking exercise for estimating the permeability of the Grimsel granodiorite - Part 2: modeling, microstructures and complementary data
Frictional properties and 3-D stress analysis of the southern Alpine Fault, New Zealand
Conversion of wet glass to melt at lower seismogenic zone conditions: Implications for pseudotachylyte creep
Rock friction under variable normal stress
The transition from frictional sliding to shear melting in laboratory stick-slip experiments
Earthquake source properties from instrumented laboratory stick-slip
Earthquake source properties from pseudotachylite
Gallery of melt textures developed in Westerly Granite during high-pressure triaxial friction experiments
Effective stress, friction and deep crustal faulting
The role of fluid pressure on frictional behavior at the base of the seismogenic zone
Earthquake forewarning in the Cascadia region
Related Content
- Publications
Filter Total Items: 35
KG²B, a collaborative benchmarking exercise for estimating the permeability of the Grimsel granodiorite - Part 1: measurements, pressure dependence and pore-fluid effects
Measuring the permeability of tight rocks remains a challenging task. In addition to the traditional sources of errors that affect more permeable formations (e.g. sample selection, non-representative specimens, disturbance introduced during sample acquisition and preparation), tight rocks can be particularly prone to solid–fluid interactions and thus more sensitive to the methods, procedures and tAuthorsChristian David, J. Wasserman, F. Amann, David A. Lockner, E.H. Rutter, T Vanorio, A. Amann Hildenbrand, J. Billiotte, T. Reuschle, D. Lasseux, J. Fortin, R. Lenormand, A.P.S. Selvadurai, P.G. Meredith, J. Browning, T.M. Mitchell, D. Loggia, F. Nono, J. Sarout, L. Esteban, C. Davy, L. Louis, G. Boitnott, C. Madonna, E. Jahns, Fleury. M., G. Berthe, P. Delage, P. Braun, D. Grégoire, L. Perrier, P. Polito, Y. Jannot, A. Sommier, B. Krooss, R. Fink, Q. Hu, J.M. Klaver, A. ClarkKG²B, a collaborative benchmarking exercise for estimating the permeability of the Grimsel granodiorite - Part 2: modeling, microstructures and complementary data
Measuring and modelling the permeability of tight rocks remains a challenging task. In addition to the traditional sources of errors that affect more permeable formations (e.g. sample selection, non-representative specimens, disturbance introduced during sample acquisition and preparation), tight rocks can be particularly prone to solid–fluid interactions and thus more sensitive to the methods, prAuthorsChristian David, J. Wassermann, F. Amann, J.M. Klaver, C. Davy, J. Sarout, L. Esteban, E.H. Rutter, Q. Hu, L. Louis, P. Delage, David A. Lockner, A.P.S. Selvadurai, T Vanorio, A. Amann Hildenbrand, P.G. Meredith, J. Browning, T.M. Mitchell, C. Madonna, J. Billiotte, T. Reuschle, D. Lasseux, J. Fortin, R. Lenormand, D. Loggia, F. Nono, G. Boitnott, E. Jahns, Fleury. M., G. Berthe, P. Braun, D. Grégoire, L. Perrier, P. Polito, Y. Jannot, A. Sommier, B. Krooss, R. Fink, A. ClarkFrictional properties and 3-D stress analysis of the southern Alpine Fault, New Zealand
New Zealand's Alpine Fault (AF) ruptures quasi-periodically in large-magnitude earthquakes. Paleoseismological evidence suggests that about half of all recognized AF earthquakes terminated at the boundary between the Central and South Westland sections of the fault. There, fault geometry and the polarity of uplift change. The South Westland AF exhibits oblique-normal fault motion on a structure orAuthorsCarolyn Boulton, Nicolas C. Barth, Diane E. Moore, David A. Lockner, John Townend, Daniel R. FaulknerConversion of wet glass to melt at lower seismogenic zone conditions: Implications for pseudotachylyte creep
Coseismic frictional melting and the production of quenched glass called pseudotachylyte is a recurring process during earthquakes. To investigate how glassy materials affect the postseismic strength and stability of faults, obsidian gouges were sheared under dry and wet conditions from 200°C to 300°C at ~150 MPa effective normal stress. Dry glass exhibited a brittle rheology at all conditions tesAuthorsBrooks P. Proctor, David A. Lockner, Jacob B. Lowenstern, Nicholas M. BeelerRock friction under variable normal stress
This study is to determine the detailed response of shear strength and other fault properties to changes in normal stress at room temperature using dry initially bare rock surfaces of granite at normal stresses between 5 and 7 MPa. Rapid normal stress changes result in gradual, approximately exponential changes in shear resistance with fault slip. The characteristic length of the exponential changAuthorsBrian D. Kilgore, Nicholas M. Beeler, Julian C. Lozos, David OglesbyThe transition from frictional sliding to shear melting in laboratory stick-slip experiments
No abstract availableAuthorsDavid A. Lockner, Brian D. Kilgore, Nicholas M. Beeler, Diane E. MooreEarthquake source properties from instrumented laboratory stick-slip
Stick-slip experiments were performed to determine the influence of the testing apparatus on source properties, develop methods to relate stick-slip to natural earthquakes and examine the hypothesis of McGarr [2012] that the product of stiffness, k, and slip duration, Δt, is scale-independent and the same order as for earthquakes. The experiments use the double-direct shear geometry, Sierra WhiteAuthorsBrian D. Kilgore, Arthur F. McGarr, Nicholas M. Beeler, David A. LocknerEarthquake source properties from pseudotachylite
The motions radiated from an earthquake contain information that can be interpreted as displacements within the source and therefore related to stress drop. Except in a few notable cases, the source displacements can neither be easily related to the absolute stress level or fault strength, nor attributed to a particular physical mechanism. In contrast paleo-earthquakes recorded by exhumed pseudotaAuthorsNicholas M. Beeler, Giulio Di Toro, Stefan NielsenGallery of melt textures developed in Westerly Granite during high-pressure triaxial friction experiments
IntroductionMelting occurred during stick-slip faulting of granite blocks sheared at room-dry, room-temperature conditions in a triaxial apparatus at 200–400 megapascals (MPa) confining pressure. Petrographic examinations of melt textures focused largely on the 400-MPa run products. This report presents an overview of the petrographic data collected on those samples, followed by brief descriptionsAuthorsDiane E. Moore, David A. Lockner, Brian D. Kilgore, Nicholas M. BeelerEffective stress, friction and deep crustal faulting
Studies of crustal faulting and rock friction invariably assume the effective normal stress that determines fault shear resistance during frictional sliding is the applied normal stress minus the pore pressure. Here we propose an expression for the effective stress coefficient αf at temperatures and stresses near the brittle-ductile transition (BDT) that depends on the percentage of solid-solid coAuthorsN.M. Beeler, Greg Hirth, Amanda M. Thomas, Roland BurgmannThe role of fluid pressure on frictional behavior at the base of the seismogenic zone
To characterize stress and deformation style at the base of the seismogenic zone, we investigate how the mechanical properties of fluid-rock systems respond to variations in temperature and strain rate. The role of fluids on the processes responsible for the brittle-ductile transition in quartz-rich rocks has not been explored at experimental conditions where the kinetic competition between microcAuthorsGreg Hirth, Nicholas M. BeelerEarthquake forewarning in the Cascadia region
This report, prepared for the National Earthquake Prediction Evaluation Council (NEPEC), is intended as a step toward improving communications about earthquake hazards between information providers and users who coordinate emergency-response activities in the Cascadia region of the Pacific Northwest. NEPEC charged a subcommittee of scientists with writing this report about forewarnings of increaseAuthorsJoan S. Gomberg, Brian F. Atwater, Nicholas M. Beeler, Paul Bodin, Earl Davis, Arthur Frankel, Gavin P. Hayes, Laura McConnell, Tim Melbourne, David H. Oppenheimer, John G. Parrish, Evelyn A. Roeloffs, Gary D. Rogers, Brian L. Sherrod, John Vidale, Timothy J. Walsh, Craig S. Weaver, Paul M. Whitmore