Jonathan M. Lees

University of North Carolina at Chapel Hill

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J. B. Johnson

Boise State University

Daniel Bowman

Sandia National Laboratories

Mario Ruiz

Instituto Geofísico de la Escuela Politécnica Nacional

Oliver D. Lamb

GNS Science

J. J. Lyons

Alaska Volcano Observatory

Michael Shore

University of North Carolina at Chapel Hill

R. W. Sanderson

University of California, Santa Barbara

Luis Franco

Fundación Universitaria de Ciencias de la Salud

G. P. Waite

Michigan Technological University

A. Ozerov

Institute of Volcanology and Seismology

Cooperative Institutions

University of North Carolina at Chapel Hill

United States Geological Survey

University of Alaska Fairbanks

Los Alamos National Laboratory

Sandia National Laboratories California

Yale University

Russian Academy of Sciences

New Mexico Institute of Mining and Technology

The University of Tokyo

California Institute of Technology

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Thermal modeling of subducted plates: tear and hotspot at the Kamchatka corner

Earth and Planetary Science Letters (2004)

Anne Davaille Jonathan M. Lees

Pacific Plate

Slab window

Hotspot (geology)

Convergent boundary

10.1016/j.epsl.2004.07.024

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Citations (57)

Three‐dimensional attenuation tomography at Loma Prieta: Inversion of t^* for Q

Journal of Geophysical Research Atmospheres (1994)

Jonathan M. Lees Grant T. Lindley

Three‐dimensional Q −1 variations in the aftershock region of Loma Prieta are derived by tomographic inversion. The data set consists of over 4000 aftershock recordings at 22 PASSCAL (Program for Array Seismic Studies of the Continental Lithosphere) stations deployed after the Loma Prieta mainshock of 1989. Estimates of attenuation are determined from nonlinear least squares best fits to the Fourier amplitude spectrum of P and S wave arrivals. The linear attenuation inversion is accomplished by using three‐dimensional velocity variations derived previously in nonlinear velocity inversions. Low Q is observed near the surface and Q generally increases with depth. The southwest side of the San Andreas fault exhibits lower Q than does the northeast side and this feature apparently extends to approximately 7 km depth. The fault zone, as determined by the dipping plane of aftershock activity, is characterized by slightly higher Q p and lower Q s , compared to regions immediately adjacent to the fault. These correlate with high‐velocity anomalies associated with seismicity at depth. The results are in agreement with earlier observations regarding the association of high‐velocity anomalies, seismicity, and fault zone asperities.

Seismic Tomography

Fault plane

10.1029/93jb03460

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Citations (92)

Intrinsic and scattering attenuation of the Mt Fuji Region, Japan

Carolina Digital Repository (University of North Carolina at Chapel Hill) (2009)

TH Chung Jonathan M. Lees Keitaro Yoshimoto Eisuke Fujita Motoo Ukawa

10.17615/a66v-wz09

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On the stability of P-wave tomography at Loma Prieta: A comparison of parameterizations, linear and nonlinear inversions

Bulletin of the Seismological Society of America (1992)

Jonathan M. Lees E. Shalev

We investigate the stability of tomographic analysis by comparing the results of two different methods of parameterizing the three-dimensional P -wave velocity variations in the vicinity of the 1989 Loma Prieta earthquake. A block inversion is implemented using 55 by 45 by 10 blocks of 1 km width and varying thickness to a depth of 25 km below the surface. Linear and nonlinear analysis are presented. The nonlinear analysis is achieved by iterating over three-dimensional raytracing and earthquake relocation relative to current three-dimensional models until solutions show only small improvements. A second parameterization is achieved by using cubic B-spline functions to span the space of the model, which is rotated by 46.5°. Nonlinear results are presented with several different starting models illustrating the robustness of the technique to the initial conditions. All the nonlinear results produced essentially the same final model, which was structurally the same as the model obtained by linear analysis using a reasonable starting model.

Nonlinear model

10.1785/bssa0820041821

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Citations (21)

Dissection of a composite volcanic earthquake at Santiaguito, Guatemala

Geophysical Research Letters (2009)

J. B. Johnson R. W. Sanderson J. J. Lyons R. P. Escobar-Wolf G. P. Waite

Volcano earthquake sources associated with eruptions at Santiaguito volcano in Guatemala are complex. Rock fracture, fluid flow, and gas expansion occur at variable time scales and induce superposed ground motions, including both static and dynamic deformation, and atmospheric pressure disturbances. Dissection of this composite event is facilitated through extra‐seismic observations, such as infrasound, geodetic, and visual monitoring. Multi‐parametric investigation of an eruptive event on Jan. 4th 2009 reveals increased degassing, apparent as both geodetic tilt and harmonic seismo‐infrasonic tremor, preceding an explosive event. The explosive event itself entails surface dome uplift, multiple eruptive pulses, and subsequent re‐equilibration of the volcanic edifice manifested in derived tilt. We report here on an integrated approach to discerning the physical processes at the actively effusing and exploding Santiaguito volcano and describe the composite earthquake that occurs here.

Tiltmeter

Seismogram

10.1029/2009gl039370

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Citations (26)

Prospects for infrasound bolide detections from balloon-borne platforms

EGU General Assembly Conference Abstracts (2017)

Eliot Young Daniel Bowman Stephen Arrowsmith Marc Boslough Viliam Klein

Source

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A statistical technique for validating velocity models

Bulletin of the Seismological Society of America (1996)

Edwin S. Iversen Jonathan M. Lees

Abstract This study investigates the use of a station influence statistic to identify velocity model shortcomings in the earthquake hypocenter location problem. Two groups of microearthquake events are examined. The first is a group of 81 events from the Mount St. Helens region that occurred between November 1987 and September 1991; the second, 110 well-located events from the 1992 Joshua Tree after-shock sequence. We describe a method for validating a postulated earth model. Let λ denote the hypocenter estimates that Geiger's method obtains. Systematically remove each station observation from the location problem, and recompute the location estimate. Call this estimate λ(i) when the ith station is removed. For a single event, define a station's influence (SI) as a weighted difference between λ and λ(i). Distributional summaries of SI statistics across events are used to identify model shortcomings: Given a specified velocity model, SI distributions that are not homogeneous across stations provide evidence of model inadequacies and/or failures in the weighting scheme. We show that velocity model shortcomings detected using SI statistics for the Mount St. Helens sequence under a one-dimensional model appear to correlate with known physical anomalies; while SI distributions evaluated under a three-dimensional model are more homogeneous and reflect a modest improvement over the one-dimensional model. SI distributions provide evidence of model failure for the Joshua Tree sequence under a one-dimensional model, but no evidence of failure under a three-dimensional model. Finally, the weighting scheme's validity is verified for the Joshua Tree sequence under the three-dimensional model.

Hypocenter

Sequence (biology)

Statistic

Tree (set theory)

10.1785/bssa0860061853

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Citations (5)

zoeppritz: Seismic Reflection and Scattering Coefficients

Jonathan M. Lees

Reflection

10.32614/cran.package.zoeppritz

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