Scientific and Technical Aerospace Reports Volume 38 July 28, 2000

To investigate the effects of changes in the latitudinal temperature gradient and the global mean temperature on dust concentration
in the Northern Hemisphere, experiments with the Goddard Institute for Space Studies General Circulation Model
(GISS GCM) are performed. The dust concentration over Greenland is calculated from sources in central and eastern Asia, which
are integrated on-line in the model. The results show that an increase in the latitudinal temperature gradient increases both the
Asian dust source strength and the concentration over Greenland. The source increase is the result of increased surface winds, and
to a minor extent, the increase in Greenland dust is also associated with increased northward transport. Cooling the climate in
addition to this increased gradient leads to a decrease in precipitation scavenging, which helps produce a further (slight) increase
in Greenland dust in this experiment. Reducing the latitudinal gradient reduces the surface wind and hence the dust source, with
a subsequent reduction in Greenland dust concentrations. Warming the climate in addition to this reduced gradient leads to a further
reduction in Greenland dust due to enhanced precipitation scavenging. These results can be used to evaluate the relationship
of Greenland ice core temperature changes to changes in the latitudinal and global temperatures.
Author
Deposition; Greenland; Soils; Temperature Gradients; Dust; Atmospheric General Circulation Models; Asia; Latitude
20000064052 Indiana Univ., Dept. of Geological Sciences, Bloomington, IN USA
Innovative Seismic Array Analysis for Studies of Wave Propagation in the Earth Final Report, 1 May 1995 - 30 Apr. 1999
Pavlis, Gary L.; Apr. 30, 1999; 44p; In English
Contract(s)/Grant(s): F49620-95-1-0366
Report No.(s): AD-A376283; AFRL-SR-BL-TR-00-0144; No Copyright; Avail: CASI; A01, Microfiche; A03, Hardcopy
We have developed a new seismic array data processing method to produce slowness vector estimates and an objective measure
of their uncertainties in tile form of statistical confidence intervals. The slowness vector, which is typically transformed into
bearing and velocity, is a key parameter used for identifying seismic phases and for event source location. Our method, multiwavelet
beamforming, is closely related to both time-domain and frequency-domain beamforming. The major advantage of multiwavelet
beamforming is that it produces multiple estimates of the slowness vector that are approximately statistically independent.
First, a set of wavelet transforms is applied to the data in a manner analogous to the use of the windowed Fourier transform. Next,
for each wavelet transform, we calculate semblance, a measure of signal coherence, for a range of possible slowness vectors. Then,
the slowness vector estimate associated with that transform is the vector that produces the largest semblance value. The multiple
slowness vector estimates can be treated as samples from a probability distribution, whose ”center” we estimate using the mean,
the median, and an M-estimator. Uncertainty intervals are calculated for these estimators by applying the jackknife statistical
method. The intervals for the mean estimator appear to be true statistical confidence intervals, but the estimates can be biased by
a directional noise field in low signal-to-noise circumstances. The median estimates are less biased by a directional noise field,
but sometimes underestimate the uncertainty. The M-estimator produces less-biased estimates while appearing to estimate correctly
their uncertainty.
DTIC
Seismology; Data Processing; Antenna Arrays; Beamforming
20000064068 Scripps Institution of Oceanography, Cecil H. and Ida M. Green Inst. of Geophysics and Planetary Physics, La Jolla,
CA USA
One Century of Tectonic Deformation Along the Sumatran Fault from Triangulation and GPS Surveys
Prawirodirdjo, L., Scripps Institution of Oceanography, USA; Bock, Y., Scripps Institution of Oceanography, USA; Genrich, J.
F., Scripps Institution of Oceanography, USA; Puntodewo, S. S. O., Badan Koordinasi Survey dan Permetaan Nasional, Indonesia;
Rais, J., Badan Koordinasi Survey dan Permetaan Nasional, Indonesia; Subarya, C., Badan Koordinasi Survey dan Permetaan
Nasional, Indonesia; Sutisna, S., Badan Koordinasi Survey dan Permetaan Nasional, Indonesia; May 04, 2000; 52p; In English;
Original contains color illustrations
Contract(s)/Grant(s): NAGW-2641; NSF EAR-88-17067; NSF EAR-90-04376; No Copyright; Avail: CASI; A04, Hardcopy;
A01, Microfiche
An analysis combining historical triangulation and recent Global Positioning System (GPS) survey measurements in West
and North Sumatra, Indonesia, reveals a detailed slip history along the central part of the Sumatran Fault. The arc-parallel components
of the combined velocity field are consistent with slip rates inferred from GPS data, ranging from 23 to 24 mm/yr. Between
1.0 S and 1.3 N the Sumatran Fault appears to be characterized by deep locking depths, on the order of 20 km, and the occurrence
of large (M (sub w) approximately 7) earthquakes. The long-term (1883-1993) strains show simple right-lateral shear, with rates
similar to GPS-measured, 1989-1993 strain rates. Coseismic deformation due to the 1892 Tapanuli and 1926 Padang Panjang
earthquakes, estimated from triangulation measurements taken before and after the events, indicate that the main shocks were
significantly larger than previously reported. The 1892 earthquake had a likely magnitude of M (sub w) approximately equal to
130