Raúl Madariaga

Laboratoire de Géologie de l’École Normale Supérieure

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Sergio Ruiz

University of Chile

Jaime Campos

University of Chile

C. Vigny

Laboratoire de Géologie de l’École Normale Supérieure

Alexandre Schubnel

Université Paris Sciences et Lettres

Elisa Buforn

Universidad Complutense de Madrid

Harsha S. Bhat

Laboratoire de Géologie de l’École Normale Supérieure

Agustín Udías

Universidad Complutense de Madrid

Eiichi Fukuyama

National Research Institute for Earth Science and Disaster Resilience

Felipe Leyton

University of Chile

Juan Carlos Báez

University of Chile

Cooperative Institutions

Centre National de la Recherche Scientifique

Institut de physique du globe de Paris

University of Chile

Université Paris Cité

Laboratoire de Géologie de l’École Normale Supérieure

École Normale Supérieure - PSL

Institut de Recherche pour le Développement

Universidad Nacional Autónoma de México

Institut des Sciences de la Terre

Université Paris Sciences et Lettres

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Magnitude Scaling of Early-Warning Parameters for the Mw 7.8 Tocopilla, Chile, Earthquake and Its Aftershocks

Bulletin of the Seismological Society of America (2011)

M. Lancieri A. Fuenzalida Sergio Ruiz Raúl Madariaga

We studied the correlation between the final event magnitude and four parameters obtained from the early portion of P and S phases for a set of high quality subduction events.These relationships are used in the framework of earthquake earlywarning systems for real-time magnitude estimation.The investigated parameters are the low-pass-filtered peak displacement (PD), the integral of the velocity squared (IV2), and the predominant and characteristic periods (τ p and τ c ).We created a dataset from the continuous records of the first two weeks following the 14 November 2007 M w 7.8 Tocopilla (Chile) earthquake.The dataset includes 69 events with magnitudes greater than 4, among them the main event (M w 7.8), the main aftershocks of M w 6.7 occurred on November 15, and 4 events with magnitude greater than 6.The low-pass-filtered PD read on short P-phase and S-phase windows is well correlated with the final magnitude, confirming previous results.Indeed when examining 2-s time windows of P waves, we did not observe any saturation effect for magnitudes greater than 6.5; however, there is a slope change in the regression curve.A similar result is obtained from the integral of squared velocity computed over short windows around P and S waves.The characteristic and predominant periods are correlated with magnitudes up to M w 6; but they clearly do not scale with the magnitude for the stronger events.Our observations offer insight into the feasibility of an early-warning system in Chile.

Earthquake magnitude

Earthquake warning system

10.1785/0120100045

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Citations (27)

Dominantly Aseismic Nucleation of Laboratory Earthquakes: A Quantitative Investigation

arXiv (Cornell University) (2021)

Samson Marty Harsha S. Bhat Jérôme Aubry Eiichi Fukuyama Raúl Madariaga

Decades of seismological observations have highlighted the variability of foreshock occurrence prior to natural earthquakes, making thus difficult to track how earthquakes start. Here, we report on three stick-slip experiments performed on cylindrical samples of Indian metagabbro under upper crustal stress conditions (30-60 $MPa$). Acoustic emission activity (AE) was continuously recorded by 8 calibrated acoustic sensors during the experiments, and the seismological parameters (moment magnitude, corner frequency and stress-drop) of the detected AEs were estimated. The scaling law between moment magnitude and corner frequency that characterizes natural earthquakes also applies to the detected AEs ($-8.8 \leq Mw \leq -7 $. Precursory AE activity is systemically detected during the pre-failure period, increases towards failure and is found to be driven by along fault slip velocity. Consistently for all three experiments, the stacked AE sequences follow an inverse power law of the time to failure. Decreasing fault strength heterogeneity promotes, on average, AEs migration towards zones where stick-slip events initiate. Overall, the seismic component of the pre-failure phase differs by several orders of magnitude from the aseismic component. Our observations suggest that, in this particular experimental setting, precursory AE activity is predominantly triggered by the larger nucleation phase of the upcoming stick-slip event which is an almost fully aseismic process.

Acoustic Emission

Moment magnitude scale

Source

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Source Mechanisms of Earthquakes: Theory and Practice

Agustín Udías Raúl Madariaga Elisa Buforn

This book presents an innovative new approach to studying source mechanisms of earthquakes, combining theory and observation in a unified methodology, with a key focus on the mechanics governing fault failures. It explains source mechanisms by building from fundamental concepts such as the equations of elasticity theory to more advanced problems including dislocation theory, kinematic models and fracture dynamics. The theory is presented first in student-friendly form using consistent notation throughout, and with full, detailed mathematical derivations that enable students to follow each step. Later chapters explain the widely-used practical modelling methods for source mechanism determination, linking clearly to the theoretical foundations, and highlighting the processing of digital seismological data. Providing a unique balance between application techniques and theory, this is an ideal guide for graduate students and researchers in seismology, tectonophysics, geodynamics and geomechanics, and a valuable practical resource for professionals working in seismic hazard assessment and seismic engineering.

Geomechanics

Source

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Citations (52)

Two-dimensional asymptotic iterative elastic inversion

Geophysical Journal International (1992)

Side Jin Raúl Madariaga J. Virieux Gilles Lambaré

An asymptotic linearized iterative elastic inversion method is proposed to invert 2-D Earth parameters from multicomponent data and is tested numerically. The forward problem is solved by a combination of the Born approximation and ray theoretical methods. We express the perturbed seismogram in terms of perturbations of P- and S-wave impedances and density. The inversion method is based on generalized least squares. We introduce a special form of the ℓ2 norm with a weighting function that corrects for geometrical spreading and obliquity of the reflectors. The Hessian for this norm could be estimated in a closed form that is asymptotically valid at high frequencies. We propose a quasi-Newtonian iterative method for the solution of the inverse problem. The first iteration of this inversion method resembles the operator proposed by Beylkin (1985) and Beylkin & Burridge (1990) for the asymptotic inversion of seismic data. Our method is more general than theirs because it can handle arbitrary discrete distributions of sources and receivers. Elastic inversion is generally ill-posed because the problem is overdetermined but undersampled. We study the resolution of the asymptotic inversion method for general sets of sources and receivers. We show that simultaneous inversion for both P- and S-wave impedance is generally ill-conditioned if data for a single scattering mode are available. In particular, it seems that only one parameter can be reliably resolved from marine data. Simultaneous inversion for a finite set of parameters can be resolved only for multicomponent elastic data containing both P-wave and S-wave information. Inversion tests using synthetic data calculated by finite-differences demonstrates that it is possible to invert simultaneously for P and S impedances.

Overdetermined system

Hessian matrix

Seismogram

Inverse transform sampling

10.1111/j.1365-246x.1992.tb04637.x

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Citations (159)

Effect of normal stress during rupture propagation along nonplanar faults

Journal of Geophysical Research Atmospheres (2002)

Hideo Aochi Raúl Madariaga Eiichi Fukuyama

We study a symmetrical three‐forked shear fault under simple triaxial stress. Rupture initiates in the central primary plane and propagates toward the branching point. One of the two branches is in the compressional quadrant, while the other is in the tensional domain. We study the following question: Does rupture always prefer propagating along the tensional branch because of the effect of normal stress? When the primary plane is located in the most favorable direction as determined by Mohr‐Coulomb criterion, one finds that the compressional branch is almost always preferred for various dynamic coefficients and confining pressures. Simultaneous rupture propagation on both branches appears only under a very special condition found by Aochi et al. [2000b] . These results indicate that shear stress changes produced by the rupture front dominate during dynamic rupture propagation, compared to normal stress changes. This result depends completely on the orientation of the whole fault system. In all cases, we can explain the branch selection by analyzing the applied initial shear stress and the fault properties. Change of normal stress may play a role similar to shear stress change for disjoint faults since the effect of normal stress change sometimes dominates.

Fault plane

10.1029/2001jb000500

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Citations (67)

Reawakening of large earthquakes in south central Chile: The 2016 M_w 7.6 Chiloé event

Geophysical Research Letters (2017)

Sergio Ruiz Marcos Moreno Daniel Melnick Francisco del Campo Piero Poli

Abstract On 25 December 2016, the M w 7.6 Chiloé earthquake broke a plate boundary asperity in south central Chile near the center of the rupture zone of the M w 9.5 Valdivia earthquake of 1960. To gain insight on decadal‐scale deformation trends and their relation with the Chiloé earthquake, we combine geodetic, teleseismic, and regional seismological data. GPS velocities increased at continental scale after the 2010 Maule earthquake, probably due to a readjustment in the mantle flow and an apparently abrupt end of the viscoelastic mantle relaxation following the 1960 Valdivia earthquake. It also produced an increase in the degree of plate locking. The Chiloé earthquake occurred within the region of increased locking, breaking a circular patch of ~15 km radius at ~30 km depth, located near the bottom of the seismogenic zone. We propose that the Chiloé earthquake is a first sign of the seismic reawakening of the Valdivia segment, in response to the interaction between postseismic viscoelastic relaxation and changes of interseismic locking between Nazca and South America.

10.1002/2017gl074133

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Citations (33)

The Balance Process in Subduction Zones

Cristián E. Siegel Patricio Toledo Sebastián Riquelme Raúl Madariaga Jaime Campos

The subduction zone seismic-cycle is a complex phenomena with individual earthquakes as clearer manifestations. Although earthquakes are fundamentally space-extended, they are inferred to be material ruptures mostly considered as points in space. Nevertheless, in the temporal dimension, because they are plate-velocity dependent, it is less clear that they can be considered as point processes. Therefore, when considering this plate velocity in the balance analysis and assuming a locally homogeneous stochastic process hypothesis along coarse-graining upscaling it is possible to get a picture that makes sense of the whole seismic-cycle. This picture has emergent properties not available from purely seismic events, but that are more and more frequently recognized from geodetic and satellite observations, such as distant interactions and slow slip events. Taking advantage of the instrumentation installed at northern Chile, which makes use of both temporary and permanent stations from the National Seismological Center and IPOC it has been possible to obtain a well detailed picture of the seismic cycle between 2007 and 2023, that is consistent with representations obtained from geodesical measurements. We also obtain this representation for 49-year ISC catalog. We discuss possible applications of this seismic cycle representation.

10.5194/egusphere-egu24-20904

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Long-term triggered seismicity on the Mosha fault by Damavand volcano, Iran: Implications on the seismic hazard of Tehran metropolis

Frontiers in Earth Science (2022)

Seyyedmaalek Momeni Raúl Madariaga

The seismic history of the Mosha fault, the largest and most active fault of Eastern Tehran metropolis, and its relation to the Damavand active volcano, the highest mountain in the Middle East, is investigated. We deduce that the central Mosha, near the Damavand, has a higher seismicity than either its western or eastern segments. On 7 May 2020, an Mw 5.1 earthquake occurred on the central Mosha, about 40 km east of Tehran and 10 km southwest of the Damavand crest, and it was felt intensely in Tehran. Its rupture is imaged and located in a region that presented a relative seismic quiescence compared to its eastern and western parts, during the last 14 years, suggesting its partial locking and heterogeneous distribution of fault frictional strength on this segment of Mosha. Its significant directivity to the west is confirmed by the mainshock rupture model, its PGA distribution, and distribution of early aftershocks. The rupture model suggests a relatively small stress drop of 2.6 bar, which is consistent with the comparatively high rupture dimension of 9 km for a Mw 5.1 earthquake, and indicates the easy rupture expansion on the central Mosha near the Damavand Volcano. The central Mosha experienced earthquakes in 1930, 1955, and 1983, as well as high microseismic activity and the 2020 seismic sequence, all of which strongly point to a possible influence of the Damavand Volcano on the seismicity of the central Mosha. This is corroborated by the observation of hydrothermal zones on the Mosha fault and the extension of a sill-like Damavand young magma chamber until central Mosha in tomography studies. We propose that the existing heat may increase the pore pressure on the fault, which lowers the effective normal stress, facilitates the nucleation-expansion of the rupture, and unclamps the fault. Damavand could act as a fuse and nucleate earthquakes, and if the rupture extends toward the west, it could have a significant directivity effect on low-frequency seismic waves that reach Tehran without attenuation and affect tall structures. In addition, high site amplification for frequencies up to 16 Hz due to the deep sedimentary basin, mainly in the mid-city of Tehran, will be remarkable for short buildings.

North Anatolian Fault

10.3389/feart.2022.945297

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Citations (8)

Fast and Slow Subduction Earthquakes in Latin America

Annual Review of Earth and Planetary Sciences (2025)

Sergio Ruiz Satoshi Ide Bertrand Potin Raúl Madariaga

Most seismicity in Latin America is controlled by the subduction process. Different zones have hosted earthquakes of magnitudes larger than Mw 8.5 that repeat every several centuries. Events around Mw 8.0 are more frequent; since the beginning of the twentieth century, some collocated earthquakes have occurred with differences of decades, which allows for comparison of old and modern seismological records. The rupture zones that have hosted mega-earthquakes continue to produce smaller earthquakes after three centuries. Therefore, the process of unlocking in the Latin America subduction zone occurs by giant (≥Mw 9.0), mega- (9.0 > Mw ≥ 8.5), and large (8.5 > Mw ≥ 7.5) earthquakes, and interaction between these events is not yet fully understood. We have less understanding of the earthquakes that occurred in the oceanic plates, which have not been correctly recorded due to poor seismological instrumentation and lack of knowledge about subduction during the first half of the twentieth century in Latin America. Slow earthquakes have been observed in some zones of Latin America, several of them with recurrence periods of a few years, as well as tectonic (nonvolcanic) tremors and low-frequency and very low-frequency earthquakes. How do these slow slip manifestations relate to ordinary earthquakes? This question is still difficult to answer for Latin America given the lack of dense geodetic and seismic networks that allow identification of all the slow earthquakes that likely occur more frequently than currently reported. ▪ Latin America subduction zones share similar seismic characteristics. They can host large-magnitude earthquakes and exhibit a variety of slow earthquakes. ▪ Giant earthquakes, with a magnitude greater than 9, have occurred so far in Chile, and mega-earthquakes have occurred in several Latin American countries. ▪ Additional slow earthquakes will be detected in Latin America as seismic and geodetic networks become denser.

10.1146/annurev-earth-040522-121945

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Engineering Implications of Source Parameters and 3D Wave Propagation Modeling for the 2004 Parkfield, California, Earthquake

Bulletin of the Seismological Society of America (2015)

Karin Şeşetyan Eser Çaktı Raúl Madariaga

Abstract The 2004 M w 6.0 Parkfield, California, earthquake took place in a very well‐instrumented area, producing a substantial quantity of high‐quality near‐field recordings. Taking advantage of the rare luxury of having a large number of near‐field ground‐motion recordings distributed around the fault zone and the availability of various slip models as well as an Earth structure model of the region, we study the effects of various kinematic rupture parameters to derive implications for strong ground motion simulation in engineering applications. We model the 3D wave propagation resulting from this earthquake using the 3D staggered‐grid finite‐difference method. Using a grid spacing of 100 m in our fourth‐order explicit finite‐difference code, we could properly resolve frequencies of up to 1 Hz with a minimum of eight grids per wavelength for shear waves, except in the immediate vicinity of the fault where fault‐trapped waves dominate the records. We assess the effects of various simulation parameters such as slip model, rise time (constant or variable), rupture velocity, and the earth model (1D versus 3D) on the resulting waveforms. We also investigate the distribution of engineering parameters such as peak ground velocities, peak ground displacements, and spectral accelerations at specific periods on the Earth’s surface. An outstanding feature is that at high frequencies fault‐normal components near the edge of fault segments dominate the ground‐motion field. Fault‐parallel components are dominated by lower frequencies. The difference between fault‐parallel and fault‐normal components is clearly observed in such engineering parameters as peak ground velocity and peak ground displacement.

10.1785/0120140261

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Citations (2)