2004年12月26日のスマトラ・アンダマン地震で地球が自由振動した
Jeffrey Park1, Teh-Ru Alex Song, Jeroen Tromp
1Department of Geology and Geophysics, Yale University, Post Office Box 208109, New Haven, CT 06520-8109, USA.
Science (New York, N.Y.)
|May 21, 2005
まとめ
地震破裂モデルでは,地震の自由振動は説明できるが,地質学的な移転は予測できない. 特にニコバル諸島とアンダマン諸島地域における緩やかな断層運動を理解するために,さらなる研究が必要である.
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
- テキトノフィジックスの物理学です.
背景:
- 地震フリー振動は,ハーバード・セントロイド・モーメント・テンサー (HCMT) ソリューションと比較すると,長期間 (>1000s) において異常な振幅を示します.
- HCMTのメカニズムは,通常,より短い周期 (300-500s) の表面波から派生し,長期分析の不一致につながる可能性があります.
研究 の 目的:
- 自由振動振幅を含む地震観測を正確に表す,より現実的な断層破裂モデルを開発する.
- 地震データと地質学的な移転の間の不一致を調査し,潜在的な遅い断層運動を示唆する.
主な方法:
- より急な断層の幾何学上の現実的な破裂モデルを使用しました.
- 地震波と地表波の両方から欠陥パラメータを導出しました.
- これらの洗練されたモデルを使用して,近似的な地震自由振動振幅.
主要な成果:
- 6.5 x 10^22ニュートンメートルの地震モメントを達成し,モメントマグニチュード9.15に対応しました.
- 600秒間の断裂期間を持つ断層破裂モデルは,地震観測を適切に表した.
- モデルによる地質学移転の予測不足が観察され,故障の動きが遅いことを示している.
結論:
- 精巧な破裂モデルは,標準的な方法よりも地震データに適している.
- 地質学的データは,特にニコバル諸島とアンダマン諸島の下,重大な緩やかな断層運動を示唆しています.
- 地震と地質学的観測を調和させ,複雑な断層の振る舞いを理解するために,さらなる調査が必要である.
関連する概念動画
01:21Acceleration due to Gravity on Earth
According to Newton's law of gravitation, the gravitational force on a body is proportional to its mass. According to Newton's second law of motion, the acceleration produced by an external force is inversely proportional to the force. Hence, the acceleration of an object under an external force of gravitation is independent of its mass.
The acceleration of an object close to the Earth, because of the Earth's gravitational pull, is called the acceleration due to gravity. It is always directed...
The acceleration of an object close to the Earth, because of the Earth's gravitational pull, is called the acceleration due to gravity. It is always directed...
01:20Variation in Acceleration due to Gravity near the Earth's Surface
An object's apparent weight is its weight measured by a spring balance at its location. It is different from its true weight, the force with which the Earth pulls it, because of the Earth's rotation. Mathematically, an object's apparent weight equals its true weight minus the centripetal force that keeps it in a circular motion along with the Earth's surface every 24 hours.
The difference between the true and apparent weights is proportional to the square of the Earth's angular speed. Since the...
The difference between the true and apparent weights is proportional to the square of the Earth's angular speed. Since the...
01:06Tidal Forces
The origin of Earth's ocean tides has been a subject of continuous investigation for over 2000 years. However, the work of Newton is considered to be the beginning of the proper understanding of the phenomenon. Ocean tides are the result of gravitational tidal forces. These same tidal forces are present in any astronomical body; they are responsible for the internal heat that creates the volcanic activity on Io, one of Jupiter's moons, and the breakup of stars that get too close to black holes.
01:12Measuring Acceleration Due to Gravity
Consider a coffee mug hanging on a hook in a pantry. If the mug gets knocked, it oscillates back and forth like a pendulum until the oscillations die out.
A simple pendulum can be described as a point mass and a string. Meanwhile, a physical pendulum is any object whose oscillations are similar to a simple pendulum, but cannot be modeled as a point mass on a string because its mass is distributed over a larger area. The behavior of a physical pendulum can be modeled using the principles of...
A simple pendulum can be described as a point mass and a string. Meanwhile, a physical pendulum is any object whose oscillations are similar to a simple pendulum, but cannot be modeled as a point mass on a string because its mass is distributed over a larger area. The behavior of a physical pendulum can be modeled using the principles of...
00:55Acceleration due to Gravity on Earth
Newton's second law is closely related to his first law of motion. It mathematically gives the cause-and-effect relationship between force and changes in motion. Newton's second law is quantitative and is used extensively to calculate what happens in situations involving a force. All external forces acting on a system add together to produce a net force Fnet. A larger net external force produces a larger acceleration. This acceleration is directly proportional to, and in the same direction as,...
01:28Geoid and Ellipsoid
The Earth's shape is best described as an ellipsoid, a slightly flattened sphere created by rotating an ellipse around its minor axis. This flattening results in the polar axis being about 21 kilometers shorter than the equatorial axis. In contrast, the geoid represents the Earth's gravitational shape and aligns with the mean sea level (MSL). The geoid is an irregular equipotential surface where gravity is perpendicular at every point. Variations in Earth's mass distribution cause geoid...