A data set comprising 110 spreading rates, 78 transform fault azimuths, and 142 earthquake slip vectors has been inverted to yield a new instantaneous plate motion model, designated Relative Motion 2 (RM2). The model represents considerable improvement over our previous estimate, RM1 [Minster et al., 1974]. mean averaging interval for the rate reduced less than 3 m.y. detailed comparison of RM2 with angular velocity which best fit along individual boundaries indicates that performs close...

Assuming lithospheric plates to be rigid, we systematically invert 68 spreading rates, 62 fracture zones trends and 106 earthquake slip vectors simultaneously obtain a self-consistent model of instantaneous relative motions for eleven major plates. The inverse problem is linearized solved iteratively by maximum likelihood procedure. Because the uncertainties in data are small, Gaussian statistics shown adequate. use linear theory permits (1) calculation various angular velocity caused data,...

Sources such as atmospheric or buried explosions and shallow earthquakes producing strong vertical ground displacements are known to produce pressure waves that propagate at infrasonic speeds in the atmosphere. At ionospheric altitudes low frequency acoustic coupled gravity induce variations electron density. Using Global Positioning System (GPS) data recorded by permanent GPS network operating southern California, we computed content time series for several days preceding following January...

The authors develop a method to decompose laser altimeter return waveform into series of components assuming that the position each component within can be used calculate mean elevation specific reflecting surface footprint. For simplicity, they assume is Gaussian in nature. They estimate number from inflection points smoothed copy and obtain initial estimates half-widths positions its consecutive points. Initial amplitude are obtained using nonnegative least-squares (LSM). To reduce...

Realistic anelastic attenuation laws are usually formulated as convolution operators, but this representation is intractable for time-domain synthetic seismogram methods such the finite difference method. An approach based on Padé approximants provides a convenient, accurate reformulation of general in differential form. The resulting operators form uniformly convergent sequence increasing order time derivative, and all shown to be causal, stable dissipative. In special case...

“SuomiNet,” a university-based, real-time, national Global Positioning System (GPS) network, is being developed for atmospheric research and education with funding from the National Science Foundation cost share collaborating universities. The named to honor meteorological satellite pioneer Verner Suomi, will exploit recently shown ability of ground-based GPS receivers make thousands accurate upper- lower-atmospheric measurements per day. Phase delays induced in signals by ionosphere neutral...

The southernmost San Andreas fault has a high probability of rupturing in large (greater than magnitude 7.5) earthquake sometime during the next few decades. New simulations show that chain sedimentary basins between Bernardino and downtown Los Angeles form an effective waveguide channels Love waves along southern edge Gabriel Mountains. Earthquake scenarios with northward rupture, which guided wave is efficiently excited, produce unusually long‐period ground motions over much greater...

For most solids the 'high temperature background' attenuation dominates at low frequencies and temperatures greater than about one-half melting temperature. It is likely to be important in mantle seismic frequencies. The same mechanism also contributes transient creep stresses total strains. A relaxation spectrum found which satisfies frequency dependence of laboratory Q time data. This makes it possible provide a physical interpretation parameters Jeffrey's modified Lomnitz function....

The dislocation microstructure of mantle materials can account simultaneously for long-term steady-state creep, and stress wave attenuation at seismic frequencies. hypothesis that a single microstructural model explains therheology characteristic times ranging from 1 to 1010 seconds be used restrict the class permissible rheological models mantle. W e review dam ping in order increasing complexity, reject those which do not satisfy laboratory data or geophysical constraints. This elimination...

The rate‐of‐slip vector on the San Andreas fault in central California estimated from geodetic and Holocene geological data (34 ± 3 mm/yr, N41°W 2°) is inconsistent with prediction of rigid plate models such as RM2 (56 N35°W 2°). This well‐known “San discrepancy” diagnostic deformation distributed both east Basin Range west along continental margin. We construct constraints integrated rates across these two regions consistent (1) kinematical boundary conditions imposed by model, (2)...

abstract The boundary initial value problems of elastodynamics are formulated as integral equations. It is shown that these equations may be solved by time-stepping numerical methods for the unknown values. A specific scheme presented antiplane strain and a example given.

Receiver functions are produced by deconvolving the horizontal components of a seismogram vertical component. Typically this is performed spectral division recordings single events. from events with similar backazimuth and ray parameter then stacked to improve signal-to-noise ratio. To avoid subjective time-consuming method prewhitening typically employed division, we have cast deconvolution in time domain. By performing time-domain as regularized simultaneous inversion for group that would...

Sources such as atmospheric or buried explosions and shallow earthquakes are known to produce infrasonic pressure waves in the atmosphere Because of coupling between neutral particles electrons at ionospheric altitudes, these acoustic gravity induce variations electron density. The Global Positioning System (GPS) provides a way directly measuring total content ionosphere and, therefore, detecting perturbations upper atmosphere. In July August 1996, three large surface mine blasts (1.5Kt...

In order to improve the signal-to-noise ratio of receiver function data, it is typical stack functions calculated from events at similar distances and back azimuths. We have adapted velocity spectrum stacking (VSS) technique, used extensively in reflection seismology, method data with different ray parameters, thereby improving further ratio. Perhaps more importantly, by producing stacks we take advantage differences shapes moveout curves converted phases reverberations identify separate...

Anyone who has ever taught an introductory class or talked to a general audience on plate tectonics attempted tell how the theory came about. A challenge is convey enormous excitement that characterized years of “plate revolution.” The gestation and birth this “new view Earth,” borrow term from S. Uyeda, took place merely 4 decades ago; yet it changed forever way we look not only at Earth, but also all terrestrial planets, even larger icy bodies in our solar system.

Revised estimates of seismic slip rates along the Middle America Trench are lower on average than plate convergence but match them locally (for example, Oaxaca). Along Cocos‐North American boundary this can be explained by nonuniformities in at points aseismic ridge or fracture zone subduction. For least 81 yr (and possibly several hundred years), no major ( M s ≥ 7.5) shallow earthquake is known to have occurred near Orozco Fracture Zone and Tehuantepec Ridge areas. Compared with recurrence...

A scientific publication is fundamentally an argument consisting of a set ideas and expectations supported by observations calculations that serve as evidence its veracity. An without only assertions. Consider the difference between statement “The hairy woodpecker population declining in northwest region United States” “Hairy populations States have declined 11% 1992 2003, according to data from Institute for Bird Populations (http://www.birdpop.org/).” Both or neither these statements could...

Abstract For three field seasons (2002/03, 2004/05, 2005/06) we have deployed a network of GPS receivers and seismometers around the tip propagating rift on Amery Ice Shelf, East Antarctica. During these campaigns detected seven bursts episodic propagation. To determine whether propagation events were triggered by short-term environmental forcings, analyzed simultaneous ancillary data such as wind speeds, tidal amplitudes sea-ice fraction (a proxy variable for ocean swell). We find that none...

Abstract In this article we discuss our efforts to use the NORESS array discriminate between regional earthquakes and ripple-fired quarry blasts (events that involve a number of subexplosions closely grouped in space time). The method describe is an extension time versus frequency “pattern-based” discriminant proposed by Hedlin et al. (1989b). At heart observation events tend give rise coda dominated prominent spectral features are independent periodic frequency. This character generally...

The exhaust plume of the Space Shuttle during its ascent is a very powerful source energy that excites atmospheric acoustic perturbations. Because coupling between neutral particles and electrons at ionospheric altitudes, these low frequency perturbations induce variations electron density. We computed content time series using Global Positioning System data collected on Bermuda island STS‐58 launch. analysis shows perturbation following launch lasting for 35 mn, with periods less than 10...

Abstract Previous numerical simulations (TeraShake1) of large ( M w 7.7) southern San Andreas fault earthquakes predicted localized areas strong amplification in the Los Angeles area associated with directivity and wave-guide effects from northwestward-propagating rupture scenarios. The TeraShake1 source was derived inversions 2002 7.9 Denali, Alaska, earthquake. That relatively smooth its slip distribution characteristics, owing both to resolution limits simplifications imposed by kinematic...

In this paper we consider two fundamentally different processes that can be responsible for the organization of energy in seismic coda into discrete time-independent frequency bands. One process involves resonance low velocity horizons and other requires interaction time offset wavefields produced by subevents within multiple-event mine explosions (ripple-fired quarry blasts). We examined data collected high seismometers Kazakhstan, USSR, observed regular spectral modulations resulting from...