Wave‐number frequency spectra of seismic background recordings from the large aperture seismic array (LASA) in eastern Montana have been used to study the source locations of different wave types in the frequency band from 40 to 500 mHz. Microseisms in this band consist of surface waves of the Rayleigh and Love type and compressional body, waves. The peak power band near 140 mHz (7‐sec microseisms) and the lower frequency band near 70 mHz consist of fundamental Rayleigh waves, which often come from the same direction. This is especially true for directions from coasts in the vicinity of large storms. The average directional properties of the two bands are similar, indicating coastal sources for both. Love waves and higher mode Rayleigh waves in some instances come from the same coastal directions as the fundamental mode. Compressional body wave sources, pinpointed by using horizontal phase velocity to measure range, occur near storms both in coastal and pelagic regions. Pelagic storm sources were found only at frequencies that were high compared with double the frequency of ocean waves having a group velocity equal to the storm velocity. Located in the wake of a moving storm, such sources appear to be due to the oppositely traveling waves set up when a storm moves faster than its waves.

Earth noise below 0.5 cps does not differ significantly from stationary normally distributed random noise for record lengths of the order of hours. Earthquake waves, as well as locally generated ground motion such as that due to wind, produce records which differ significantly from the above. The cross‐frequency coherence is a sensitive test for nonstationary effects such as earthquakes, and the more generalized two‐dimensional spectrum appears to be the appropriate one for looking at transient events. For stationary processes the bispectrum is a convenient method for testing nonlinear interactions, but microseisms measured so far have produced no cases of significant bispectrums.

The objective of this paper is to examine the seasonal variations in the oceans and atmosphere that force the Earth's annual wobble, and to determine whether motions of air and water are a significant source of Chandler-wobble excitation. Although our investigation is similar to the one undertaken by Munk and Hassan over 15 years ago, we come to entirely different conclusions, largely because of differences in the details of our analysis. We find that the oceans and atmosphere are not observed well enough to fully explain the annual wobble, although much of it can be accounted for by annual changes in atmospheric mass distribution and continental water storage. Near the Chandler frequency there is evidence of significant coherence between polar motion and atmospheric pressure observations for the years 1901 and 1970, suggesting that the atmosphere is important in maintaining the Chandler wobble. The magnitude of meteorological variation appears to be large enough to account for more than half, and perhaps most of the Chandler wobble variance.

Sources of earth noise have been identified and located for different parts of the frequency band from 5 to 500 mc/s. In the typical microseism bands around 75 and 150 mc/s, sources are associated with storm waves arriving at both distant and local sea coasts. During the winter months the primary‐frequency microseisms measured at La Jolla come mostly from the coast north of Cape Mendocino and are due to major storms in the North Pacific. Double‐frequency microseism sources are generally within a few hundred kilometers of La Jolla, but more distant sources have also been observed. In addition, both ocean and atmosphere produce local loading which becomes significant at frequencies below the storm microseism band.

The use of the gravity meter for measurement of ocean tides is illustrated by studies on the floating ice shelves of Antarctica. The observations are complicated by high‐frequency oscillations of the ice, attributed to oceanographic influences. Factors involved in the reduction of the gravimetric data are analyzed. Amplitude and phase are computed for the more significant tidal components, and the energy spectra from 0.03 to 4 cycles per day are presented. The Weddell Sea tide has both diurnal and semidiurnal components. The Ross Sea tide is diurnal, with the solar component predominating. The tidal range is greater in the Weddell Sea than in the Ross Sea. Correlation of tidal currents with changes in surface elevation provides an estimate of the inward dimension of the Ross Ice Shelf.