Inter- and intra-plate deformation at North American plate boundaries

Alaska tectonics and earthquake hazard studies; Southern California tectonics (block rotation); spreading near the Salton Trough; California plate motion (fault zone kinematics); and Caribbean plate motion investigations are examined

Inter- and intra-plate deformation at North American plate boundaries

A geodetic network which spans the region between San Francisco and Lake Tahoe has been measured 5 times completely with triangulation in 1880, 1922, 1929, 1943, 1963. A resurvey with the Global Positioning System (GPS) in 1991 allows the formation of 1 coseismic and 4 interseismic epochs. The data from this network provide a unique opportunity to examine the temporal and spatial evolution of the strain field associated with the 1906 San Francisco earthquake in particular and with the Pacific-North American plate boundary in general. Calculations of strain rate from the network data lead to the following conclusions. (1) There is no resolvable (greater than 0.05 microradians/yr) strain in between Sutter Buttes and the Sierra Nevada. (2) Throughout the time since the 1906 earthquake, a region extending at least as far east as the westernmost Great Valley has been undergoing deformation related to Pac:Nam interaction and the associated earthquake cycle. (3) In the time and space of overlap, our results agree with those from the United States Geological Survey (USGS) trilateration data. Both data sets indicate that strain must be accumulating to the east of Vaca. (4) The San Andreas discrepancy cannot be accommodated in the Great Valley at the 1 sigma level of our results. It is possible to absorb it in that region at the 2 sigma level. (5) Strain rate is elevated in the years following the earthquake and decays slowly with time. It is possible that the rate in the Coast Ranges increases until around 1950 and then decays. With the exception of one epoch, strain rate in the Coast Ranges is consistently fault parallel, shows no sign changes, and is consistent with monotonic strain accumulation

Kinematics of the New Zealand Plate Boundary: Relative Motion by GPS Across Networks of 1000 km and 50 km Spacing

From the 1995-97 data we are able to estimate interseismic velocities - the original aim of the project - though corrections must first be made for the coseismic effects of the Cass earthquake and postseismic effects of the Arthur's Pass event. In the following, we present four sets of results: (1) Interseismic velocities, (2) Arthur's Pass earthquake - coseismic, (3) Cass earthquake, and (4) Arthur's Pass earthquake postseismic. Work on all these fronts is still incomplete, but is being actively continued with funding from the NZ Foundation for Research, Science and Technology (FRST)

Evidence for orbital forcing of Middle Cambrian peritidal cycles: Wah Wah range, south-central Utah

We have applied a new method (gamma method) for constructing high-resolution age models to peritidal cycles in the Middle Cambrian Pierson Cove Formation (13 cycles) and the Trippe Limestone (40 cycles) exposed in the Wah Wah range, south-central Utah. Spectral analyses of the time series for the gamma age model indicate the presence of significant spectral peaks (relative to a null model) in both data sets. After experimenting with different assumptions for the duration of the mean primary or measured cycle, we found that for the Trippe data set assigning the mean duration of precession to the mean primary cycle produced a reasonably good correlation between the spectrum and the early Paleozoic estimate of insolation forcing. In particular, the periods of the three significant spectral peaks in the Trippe record correspond to estimated line periods for eccentricity and precession and a combination tone of precession. A spectrum for the Trippe cycles based on the conventional assumption that time is proportional to thickness contained only one significant peak, and reasonable estimates of the duration of the mean primary cycle produced a poor fit to the insolation model. Spectral results from the Pierson Cove cycles were less compelling, possibly because of the short length of the record. The presence in the Trippe spectrum of significant peaks with periods corresponding to high-frequency orbital variations suggests that preservation of high-frequency Milankovitch signals is more common than implied by models of shallow marine cyclicity based on Pleistocene sea-level records. The results of these spectral analyses suggest that the gamma method can be used to construct age models for peritidal carbonate cycles that are accurate enough to test for periodicity and deterministic mechanisms, even in rocks as old as the Cambrian

Evidence for orbital forcing of Middle Cambrian peritidal cycles: Wah Wah range, south-central Utah

We have applied a new method (gamma method) for constructing high-resolution age models to peritidal cycles in the Middle Cambrian Pierson Cove Formation (13 cycles) and the Trippe Limestone (40 cycles) exposed in the Wah Wah range, south-central Utah. Spectral analyses of the time series for the gamma age model indicate the presence of significant spectral peaks (relative to a null model) in both data sets. After experimenting with different assumptions for the duration of the mean primary or measured cycle, we found that for the Trippe data set assigning the mean duration of precession to the mean primary cycle produced a reasonably good correlation between the spectrum and the early Paleozoic estimate of insolation forcing. In particular, the periods of the three significant spectral peaks in the Trippe record correspond to estimated line periods for eccentricity and precession and a combination tone of precession. A spectrum for the Trippe cycles based on the conventional assumption that time is proportional to thickness contained only one significant peak, and reasonable estimates of the duration of the mean primary cycle produced a poor fit to the insolation model. Spectral results from the Pierson Cove cycles were less compelling, possibly because of the short length of the record. The presence in the Trippe spectrum of significant peaks with periods corresponding to high-frequency orbital variations suggests that preservation of high-frequency Milankovitch signals is more common than implied by models of shallow marine cyclicity based on Pleistocene sea-level records. The results of these spectral analyses suggest that the gamma method can be used to construct age models for peritidal carbonate cycles that are accurate enough to test for periodicity and deterministic mechanisms, even in rocks as old as the Cambrian

New horizons for the methodology and physiology of training periodization: Block Periodization: New horizon or a false dawn?

It would appear premature to herald block periodization as a ‘new horizon’ in training planning, partly because of a fundamental lack of supporting evidence and clearly delineated rationale, and partly because contradictory evidence exists questioning its universal efficacy in elite contexts. What block periodization does positively contribute to current planning methodologies is a more formal description of a particular planning tactic that may be advantageously added to the elite coaches menu of potential planning options. Therefore, while blocked-training schemes may be useful ploys in specific training contexts, the claim that this framework represents a new departure in training planning may be somewhat overly enthusiastic. Hence, perhaps a more appropriate description of block periodization is ‘new variation’, rather than a ‘new horizon’, in sports training planning

Are cyclic sediments periodic? Gamma analysis and spectral analysis of Newark Supergroup lacustrine strata

Methodologies are suggested for the analysis of cyclic sediments. These include (1) linear analysis to determine whether cycles are of approximately constant duration and whether the relation between thickness and time is facies dependent and (2) multiple prolate-spheroidal windowing spectral analysis to determine whether time-series data indicate periodicities, either of the primary cycles or of higher or lower orders. The results of both methods are compared to a null hypothesis as a semiquantitative test of periodicity. Application of the methods to Newark Supergroup lacustrine cycles suggests that the primary cycles are approximately periodic and record a response to astronomical precession. The time represented by a given thickness of the different facies increases with the depositional water depth of that facies and with decreasing grain size. Precessional index cycles and long-period precessional index beats, or eccentricity, are strongly recorded in the spectra. Spectral results suggest but do not prove lengthening of the periodicities of orbital parameters since 200 Ma

Are cyclic sediments periodic? Gamma analysis and spectral analysis of Newark Supergroup lacustrine strata

Methodologies are suggested for the analysis of cyclic sediments. These include (1) linear analysis to determine whether cycles are of approximately constant duration and whether the relation between thickness and time is facies dependent and (2) multiple prolate-spheroidal windowing spectral analysis to determine whether time-series data indicate periodicities, either of the primary cycles or of higher or lower orders. The results of both methods are compared to a null hypothesis as a semiquantitative test of periodicity. Application of the methods to Newark Supergroup lacustrine cycles suggests that the primary cycles are approximately periodic and record a response to astronomical precession. The time represented by a given thickness of the different facies increases with the depositional water depth of that facies and with decreasing grain size. Precessional index cycles and long-period precessional index beats, or eccentricity, are strongly recorded in the spectra. Spectral results suggest but do not prove lengthening of the periodicities of orbital parameters since 200 Ma

Rapid microplate rotations and backarc rifting at the transition between collision and subduction

ABSTRACT Using global positioning system velocities from convergent plate boundaries in Papua New Guinea, New Zealand, Tonga, Vanuatu, and the Marianas, we note a spatial correlation between rapid tectonic block rotations and the transition from subduction to collision. We present a mechanism for the block rotations, in which the change from collision of a buoyant indentor to normal subduction exerts a torque on the upper-plate microplate. This work improves our understanding of the causes of rapid vertical axis rotations, often observed in paleomagnetic studies. We also show how collision-induced rotations may lead to backarc rifting

Interim Report on Studies of the Mw ~7.9 Earthquake of 3 May 2006, Kingdom of Tonga

The very large and rare Mw ~7.9 Earthquake of 3 May 2006 in the Kingdom of Tonga aroused great interest among both Tongan scientists and their colleagues in Australia, New Zealand, and the United States. To investigate the earthquake we formed a collaborative research group of scientists from Australia, New Zealand, Tonga, and the United States. We brought in seven seismographs from Australia and the US to supplement the three-station network already in Tonga and eight GPS receivers primarily for the islands west of the earthquake epicenter. In addition, we made coastal observations to determine the regional pattern of subsidence associated with the earthquake. The GPS instruments can measure horizontal and vertical motion quite precisely, but only after the earthquake from the time of deployment onward, except for some sites on Tongatapu, Vava’u, and Lifuka that had been occupied by GPS receivers in the past. This report describes our efforts.Ministry of Lands and Survey, Kingdom of TongaGeoscience AustraliaGeological and Nuclear Sciences, New ZealandThe National Science Foundation, U.S.A.Institute for Geophysic