Geodynamics Branch research report, 1982

The research program of the Geodynamics Branch is summarized. The research activities cover a broad spectrum of geoscience disciplines including space geodesy, geopotential field modeling, tectonophysics, and dynamic oceanography. The NASA programs which are supported by the work described include the Geodynamics and Ocean Programs, the Crustal Dynamics Project, the proposed Ocean Topography Experiment (TOPEX) and Geopotential Research Mission. The individual papers are grouped into chapters on Crustal Movements, Global Earth Dynamics, Gravity Field Model Development, Sea Surface Topography, and Advanced Studies

Tsunami risk management for crustal earthquakes and non-seismic sources in Italy

publishedVersio

NASA geodynamics program investigations summaries: A supplement to the NASA geodynamics program overview

The development of a time series of global atmospheric motion and mass fields through April 1984 to compare with changes in length of day and polar motion was investigated. Earth rotation was studied and the following topics are discussed: (1) computation of atmospheric angular momentum through April 1984; (2) comparisons of psi sub values with variations in length of day obtained by several groups utilizing B.I.H., lunar laser ranging, VLBI, or Lageos measurements; (3) computation of atmospheric excitation of polar motion using daily fields of atmospheric winds and pressures for a short test period. Daily calculations may be extended over a longer period to examine the forcing of the annual and Chandler wobbles, in addition to higher frequency nutations

Earthquakes and sea-level change in Hokkaido, north-east Japan

This thesis details the results of an investigation into the pattern of relative sea-level (RSL) changes in north-east Hokkaido, Japan. The aim of the research is to better understand the importance of seismic and non-seismic processes in controlling spatial patterns of vertical land motions over a range of timescales. The main focus is on using salt-marsh sediments as a source of data to reconstruct RSL change during the current interseismic period, since c. 300 calibrated years before present (cal. yr BP). Previous research on the Pacific coast of Hokkaido suggests that this period is characterised by subsidence caused by strain accumulation on the locked part of the Pacific/North American plates. I apply foraminiferal-based methods of palaeoenvironmental reconstruction to develop, using transfer functions, quantitative reconstructions of RSL change at five sites in north-east Hokkaido. Contemporary foraminifera are zoned with respect to elevation and tidal inundation, and my preferred transfer function (a model that contains 87 samples and 24 taxa) has a prediction r2 of 0.75 and a root mean squared error of prediction of ± 0.32 m. I apply this transfer function to shallow fossil sediment sequences at five salt marshes and use a combination of 210Pb, 137Cs and tephra chronology to establish age models for the sequences. The reconstructions are consistent in demonstrating little net RSL change during the last 300-100 cal. yrs, with the exception of data from one site, Sarfutsu-toh, located on the northern tip of Hokkaido. Chronologies from two profiles developed on the Pacific coast record strong evidence for recent RSL rise since the mid-1980s, but during earlier periods of the 20th century reconstructed RSL was stable or falling. I compare my reconstructions with other direct and proxy records of land and sea-level motions. Previously published GPS and repeat levelling data indicates subsidence in south-east Hokkaido during the 20th century, although the spatial patterns and rates of change have varied. An unknown amount of this subsidence at the Kushiro tide gauge likely reflects anthropogenic activities associated with sediment compaction as well as mining-induced subsidence. An analysis of the tide-gauge records from Hokkaido show a more varied pattern of land motions, although they also confirm subsidence on the Pacific coast, close to the Kuril trench. A database of Holocene sea-level index points provides insights into longer-term millennial-scale trends in RSL. Data from six regions of Hokkaido demonstrate stable RSL close to present during the mid- and late Holocene; only the northern tip of Hokkaido (around Sarubetsu) is there evidence for a small mid-Holocene highstand of 1-3 m above present. Finally, a review of Pleistocene raised marine terrace data shows net uplift over the last c. 330 k yr, with two areas of particularly high uplift at Abashiri and on the Pacific coast near Kushiro. The evidence presented in this research demonstrates that it is incorrect to infer that the current interseismic period is characterised by subsidence. Overall, RSL has changed little in the last 300-100 cal. yrs. The subsidence recorded in the mid- and late 20th century on the Pacific coast of Hokkaido is not typical of the full interseismic period, nor can it have been sustained over Holocene or Pleistocene timescales. Limited data from previous earthquake cycles indicate that RSL was stable, rising or falling during previous interseismic intervals. These observations suggest that a representative ‘Hokkaido earthquake deformation cycle’ may not exist. Future research should better understand the controls of Quaternary volcanic activity on regional deformation patterns, and apply microfossil-based techniques to multiple earthquake cycles at sites to help define the spatial extent of land motions associated with different events

Solid earth science in the 1990s. Volume 2: Panel reports

This is the second volume of a three-volume report. Volume 2, Panel Reports, outlines a plan for solid Earth science research for the next decade. The science panels addressed the following fields: plate motion and deformation, lithospheric structure and evolution, volcanology, Earth structure and dynamics, Earth rotation and reference frames, and geopotential fields

Geodetic monitoring of tectonic deformation: Toward a strategy

Issues of interest and importance to society and science are presented. The problems considered are of national concern; their solutions may contribute to a better understanding of tectonic deformation and earthquake hazards. The need for additional field data, the role of geodetic measurements, the importance of both ground and space techniques, and the need for advanced instrumentation development are discussed

陸域および海域測地観測から推定した2011年東北地方太平洋沖地震の初期余効すべりに関する研究

Tohoku University太田雄策課

Geodynamic program office

Program activities and achievements in 1982 of the geodynamic program are summarized. The significant results presented are summarized