周囲の地震騒音からの高解像度表面波トモグラフィーです
Nikolai M Shapiro1, Michel Campillo, Laurent Stehly
1Center for Imaging the Earth's Interior, Department of Physics, University of Colorado at Boulder, Boulder, CO, USA. nshapiro@ciei.colorado.edu
まとめ
地震騒音の分析により,カリフォルニア州が明らかになった.
科学分野:
- 地質物理学 地質物理学とは地質物理学です.
- 地震学 地震学とは
- 地球科学 地球科学 地球科学
背景:
- 地球の地殻の構造を理解することは,地質学的および地震的危険性評価に不可欠です.
- 伝統的な地震画像法では,解像度やデータ取得が限られていることがあります.
研究 の 目的:
- カリフォルニアの地殻構造をイメージするための新しい方法を開発し,適用する.
- 高解像度地質物理画像の環境地震ノイズを利用する.
主な方法:
- カリフォルニアのUSArrayステーションによって記録された周囲の地震騒音は,交叉相関関係がありました.
- インターステーション経路の表面波グループ速度測定が得られました.
- カリフォルニア州の地質学単位のトモグラフィ画像は,これらの測定を用いて構築されました.
主要な成果:
- 何百もの短期間の表面波グループ速度測定が生成されました.
- トモグラフィの画像では,主要な地質学的単位が明確に描かれています.
- 低速の異常は堆積層と相関し,高速の異常は山脈の核と相関する.
結論:
- 周囲の地震騒音の交差相関は,地殻イメージングのための効果的な表面波データを提供します.
- このテクニックは,従来の方法と比較して,地殻画像の解像度と精度を向上させます.
- この研究では,地震騒音を用いてカリフォルニア州の主要な地質単位をマッピングすることに成功しました.
関連する概念動画
Travelling Waves
A wave is a disturbance that propagates from its source, repeating itself periodically, and is typically associated with simple harmonic motion. Mechanical waves are governed by Newton's laws and require a medium to travel. A medium is a substance in which a mechanical wave propagates, and the medium produces an elastic restoring force when it is deformed.
Water waves, sound waves, and seismic waves are some examples of mechanical waves. For water waves, the wave propagation medium is water;...
Water waves, sound waves, and seismic waves are some examples of mechanical waves. For water waves, the wave propagation medium is water;...
Modes of Standing Waves - I
A close look at earthquakes provides evidence for the conditions appropriate for resonance, standing waves, and constructive and destructive interference. A building may vibrate for several seconds with a driving frequency matching the building's natural frequency of vibration; this produces a resonance that results in one building collapsing while the neighboring buildings do not. Often, buildings of a certain height are devastated, while other taller buildings remain intact. This phenomenon...
Sound Waves
Sound waves can be thought of as fluctuations in the pressure of a medium through which they propagate. Since the pressure also makes the medium's particles vibrate along its direction of motion, the waves can be modeled as the displacement of the medium's particles from their mean position.
Sound waves are longitudinal in most fluids because fluids cannot sustain any lateral pressure. In solids, however, shear forces help in propagating the disturbance in the lateral direction as well. Hence,...
Sound waves are longitudinal in most fluids because fluids cannot sustain any lateral pressure. In solids, however, shear forces help in propagating the disturbance in the lateral direction as well. Hence,...
Shock Waves
While deriving the Doppler formula for the observed frequency of a sound wave, it is assumed that the speed of sound in the medium is greater than the source's speed through it. When this condition is breached, a shock wave occurs.
When the source's speed approaches the speed of sound, constructive interference between successive wavefronts emitted by the source occurs immediately behind it. Initially, scientists believed that this constructive interference would result in such high pressures...
When the source's speed approaches the speed of sound, constructive interference between successive wavefronts emitted by the source occurs immediately behind it. Initially, scientists believed that this constructive interference would result in such high pressures...
Sound as Pressure Waves
Sound waves, which are longitudinal waves, can be modeled as the displacement amplitude varying as a function of the spatial and temporal coordinates. As a column of the medium is displaced, its successive columns are also displaced. As the successive displacements differ relatively, a pressure difference with the surrounding pressure is created. The gauge pressure varies across the medium.
The pressure fluctuation depends on the difference in displacements between the successive points in the...
The pressure fluctuation depends on the difference in displacements between the successive points in the...
Echo
The human ear cannot distinguish between two sources of sound if they happen to reach within a specific time interval, typically 0.1 seconds apart. More than this, and they are perceived as separate sources.
Imagine the sound is reflected back to the ears. Assuming that the source is very close to the human, the difference between hearing the two sounds—the emitted sound and the reflected sound—may be more than the minimum time for perceiving distinct sounds. If this is the case, then the...
Imagine the sound is reflected back to the ears. Assuming that the source is very close to the human, the difference between hearing the two sounds—the emitted sound and the reflected sound—may be more than the minimum time for perceiving distinct sounds. If this is the case, then the...


