Observations of the transition from linear polarization to complex polarization in short-period compressional waves

1991 ◽  
Vol 81 (2) ◽  
pp. 611-621
Author(s):  
William Menke ◽  
Arthur Lerner-Lam
Keyword(s):  
New York ◽  
New England ◽  
Linear Polarization ◽  
Compressional Wave ◽  
P Wave ◽  
Adirondack Mountains ◽  
Compressional Waves ◽  
Short Period ◽  
Shallow Crust ◽  
Complex Polarization

Abstract We measure the polarization of compressional waves from seismograms of chemical explosion of the Ontario-New York-New England refraction experiment recorded by the seven element ECO array in the New York Adirondack mountains. After careful instrument calibration, a precision of about 5° is achieved in measuring the azimuth of the compressional wave polarization direction. The azimuth of the polarization of the onset of the P wave differs from the geometrical source-receiver azimuth by as much as 20°, possible due to deflection of the first-arriving ray by lateral variation in crustal structure. Shortly after the onset of P, the polarization changes from the linear polarization expected of a compressional wave to become very complex. The time of this transition increases with source-receiver distance, from about 0.4 to 0.5 sec at 50 km distance and 0.7 to 0.8 sec at 150 km distance. The complex polarization may be due to the arrival of strongly scattered waves that have propagated mainly in the shallow crust, which would imply that the upper 1 to 2 km of the crust is particularly heterogeneous.

STANDING‐WAVE PHENOMENA IN SHORT‐PERIOD SEISMIC NOISE

Geophysics ◽  
1965 ◽  
Vol 30 (6) ◽  
pp. 1179-1186 ◽  
Author(s):  
Indra N. Gupta
Keyword(s):  
Steady State ◽  
Standing Wave ◽  
Seismic Noise ◽  
P Wave ◽  
Stratified Medium ◽  
Alternative Theory ◽  
Compressional Waves ◽  
Short Period ◽  
Wave Phenomena ◽  
Phase Spectra

Short‐period vertical seismometers are used in deep holes at several sites to obtain the change with depth in amplitude and phase spectra of short‐period seismic noise. Although the observed spectra can be explained by an arbitrary combination of several Rayleigh modes, an alternative theory is suggested here. An attempt is made to explain both amplitude and phase spectra of observed microseisms of period less than 6 sec in terms of standing‐wave phenomena caused by steady‐state plane harmonic compressional waves propagating vertically through a horizontally stratified medium. At most sites, the observed data indicate satisfactory agreement with the expected results. A considerable fraction of the short‐period noise may, therefore, be regarded as P‐wave noise propagating vertically from below.

Fault plane solutions for northeastern United States earthquakes

1981 ◽  
Vol 71 (6) ◽  
pp. 1875-1882
Author(s):  
Jay J. Pulli ◽  
M. Nafi Toksöz
Keyword(s):  
United States ◽  
New York ◽  
New England ◽  
Fault Plane ◽  
Local Stress ◽  
P Wave ◽  
Northeastern United States ◽  
Stress Concentrations ◽  
Fault Plane Solutions ◽  
Entire Area

Abstract Fault plane solutions for eight earthquakes occurring in the northeastern United States have been determined using P-wave first motions and a computer algorithm for picking all valid solutions. The predominant mechanism in the area is thrust faulting, however the direction of the P axis is not consistent throughout the entire area. In central New England (Maine-New Hampshire), the P axis trends nearly E-W. In southeastern New England, the P axis trends N-S to NE-SW. In the Adirondacks region of New York, the P axis trends NE-SW as previously reported by Yang and Aggarwal (1981). Although the stress distribution appears to be complicated, as in the Central United States (Street et al., 1974), an underlying E-W compressive stress may exist in the New England area. These small earthquakes may represent the response to local stress concentrations.

The effects of porosity‐permeability‐clay content on the velocity of compressional waves

Geophysics ◽  
1991 ◽  
Vol 56 (12) ◽  
pp. 1930-1939 ◽  
Author(s):  
Theodoros Klimentos
Keyword(s):  
Wave Velocity ◽  
High Pressures ◽  
Clay Content ◽  
Compressional Wave ◽  
P Wave ◽  
Compressional Waves ◽  
Wide Range ◽  
Seismic Frequencies ◽  
Water Saturated ◽  
Compressional Velocity

Compressional velocities [Formula: see text] were measured in laboratory samples at ultrasonic frequencies (0.5–1.5 MHz) and under varying confining and pore fluid pressures (up to 40 MPa). Forty‐two water saturated sandstones having a range of porosities Φ (2 to 36 percent), permeabilities K (0.001 to 306 mD) and clay contents C (negligible to 30 percent) were studied. I found that at 40 MPa the compressional velocity is inversely proportional to clay content. P‐wave velocity decreases with increasing porosity, but the scatter is large even at very high pressures. The velocity‐porosity scatter is reduced when the clay content is included. The dependence of [Formula: see text] on permeability for a wide range of porosities (6 to 36 percent) is indeterminable due to a large scatter. When the rocks are grouped into identical porosities the scatter is reduced and [Formula: see text] increases with decreasing clay content and increasing permeability. However, the effect of permeability alone on [Formula: see text] was found to be negligible in rocks with identical porosity, lithology, and negligible or similar clay content. Hence, the velocity‐permeability relationship is controlled by the velocity‐clay content and permeability‐clay content interrelations. For all samples, the compressional‐wave velocity [Formula: see text] in km/s at ultrasonic frequencies and 40 MPa is related to porosity Φ (fractional), clay content C (fractional) and permeability K (millidarcy) by [Formula: see text] r = 0.96 where r is the correlation coefficient. The relationship shows empirically that the permeability effect is very small compared to that of porosity and clay content. By calculating the elastic moduli, I extrapolated from ultrasonic to seismic frequencies and obtained [Formula: see text], r = 0.93 for porosities 6–36 percent.

Google Hangout with Annie Baker, Playwright 1/25/16, 2:33 PM

2016 ◽  
Vol 69 (4) ◽  
pp. 57-64
Author(s):  
Genevieve Yue
Keyword(s):  
New York ◽  
New England ◽  
Selection Process ◽  
Pulitzer Prize ◽  
Film Festival ◽  
The Past

Genevieve Yue interviews playwright Annie Baker, whose Pulitzer Prize–winning play The Flick focuses on the young employees of a single-screen New England movie house. Baker is one of the most critically lauded playwrights to emerge on the New York theater scene in the past ten years, in part due to her uncompromising commitment to experimentation and disruption. Baker intrinsically understands that arriving at something meaningful means taking a new way. Accordingly, Baker did not want to conduct a traditional interview for Film Quarterly. After running into each other at a New York Film Festival screening of Chantal Akerman's No Home Movie (2015)—both overwhelmed by the film—Yue and Baker agreed to begin their conversation by choosing a film neither of them had seen before and watching it together. The selection process itself led to a long discussion, which led to another, and then finally, to the Gmail hangout that forms the basis of the interview.

Anthropologic Relationships among Prehistoric Northeastern Amerindians

1980 ◽  
Vol 1 (2) ◽  
pp. 145-159
Author(s):  
Edward F. Harris ◽  
Nicholas F. Bellantoni
Keyword(s):  
New York ◽  
Gene Flow ◽  
Material Culture ◽  
New England ◽  
Cultural Barriers ◽  
Group Differences ◽  
Phenetic Analysis ◽  
Trade Relationships ◽  
Good Agreement

Archaeologically defined inter-group differences in the Northeast subarea ate assessed with a phenetic analysis of published craniometric information. Spatial distinctions in the material culture are in good agreement with those defined by the cranial metrics. The fundamental dichotomy, between the Ontario Iroquois and the eastern grouping of New York and New England, suggests a long-term dissociation between these two groups relative to their ecologic adaptations, trade relationships, trait-list associations, and natural and cultural barriers to gene flow.

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