Catégorie

Sismologie

thumb|Station sismologique Basse-Terre au sommet du morne Mazeau en Guadeloupe. La sismologie ou séismologie (ce dernier est un anglicisme de seismology) est une discipline scientifique qui étudie les séismes (tremblements de terre) et la propagation des ondes élastiques (dites ondes sismiques) à l'intérieur de la Terre. La sismologie moderne utilise les concepts de la mécanique newtonienne appliqués à la connaissance de la Terre. Les principales disciplines sont la sismogenèse, la sismotectonique, la sismologie de l'ingénieur, la sismologie globale, la sismique active et la sismologie spatiale. Cette liste n'est pas exhaustive. Il existe aussi des disciplines associées où la sismologie est importante comme la paléosismologie, la mécanique des roches ou l'héliosismologie. Les tremblements de terre ont longtemps été considérés comme des messages divins. Pour les Chinois, c'était un signe que le Ciel (les dieux) désavouait la légitimité de l'empereur. En raison de la signification politique qu'accordaient les Chinois aux séismes et à leur fréquence importante dans la région, très tôt, ils notèrent consciencieusement les différents tremblements de terre. L'un des premiers à être noté est celui de 780 av. J.-C. et le pire en perte de vies humaines est celui de 1556 dans la province de Shaanxi qui fit plus de . Les Chinois n'établirent aucune théorie scientifique sur l'origine naturelle des séismes, mais c'est l'un d'entre eux, l'inventeur Zhang Heng, qui créa le premier pseudo-sismographe en 132. Né dans une région de forte sismicité, Zhang Heng mit au point un sismoscope utilisant le principe du pendule. Pour les anciens Grecs, Poséidon était le responsable de tels événements. Pourtant, cela n'empêcha pas des Grecs comme Thalès () et surtout Aristote () de penser que les séismes ont une origine naturelle. Selon Thalès, ce sont des éruptions d'eau chaude qui sont la cause des tremblements de terre : les surfaces émergés flottent sur l'eau, et des éruptions d'eau chaude assez violentes peuvent faire bouger la terre.

Ontologie

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Exercices associés (17)

Cylindre ferromagnétique

An infinite cylinder of ferromagnetic material carries a uniform magnetization

{\bf M}

. What is the current density linked to the surface of the cylinder? Determine the fields

{\bf B}

and

{\bf H}

inside and outside of the cylinder. At the surface of the magnetized cylinder a linked current whose density(current per unit length) is

{\bf K}_b=M\,{\bf \hat{\phi}}

is circulating. The surface of the cylinder is behaving like an infinite coil that carries the same current density. So

{\bf B}={\bf H}=0

Ordre de grandeur

Make some rough estimations (in terms of powers of 10) according to your “feeling” (test for a job interview as “management consultant”...):

How many pencils would you need to draw a straight line along the Earth’s equator ?
How many wedding dresses are sold every year in Italy ?
How many individual hairs are on your head ?
How many water drops are contained in all the oceans of the globe ?
How many CHF 10 banknotes have to be piled up to reach the moon ? Would a space missi

Tapis roulant

xa0 A mass m is on a conveyor on which it is subject to a dry friction force. We note the static friction coefficient α_(s) and the dynamic one α_(d). Moreover, the mass is attached to the wall by a spring of stiffness k, of length at rest l₀, and of negligible mass. We note g the acceleration of gravity.

At the initial time (tu2004=u20040), the length of the spring is equal to l₀ (i.e. the spring is at rest) and the conveyor starts its function. It drives the mass m at a constant velocity v₀

Question conceptuelle: Coriolis dans votre lavabo

Calculate the order of magnitude of the Coriolis acceleration of the water in your emptying sink. The Coriolis acceleration is expressed with the following equation:

\vec a_{\rm Coriolis}=2\vec{\Omega} \wedge \vec{V} \,

in which Ω⃗ is the Earth’s rotational velocity and V⃗ is the velocity of the water in the sink. We find the following expression for the Coriolis acceleration’s norm:

a_{\rm Coriolis}=2\Omega V \sin\theta \,

with

\Omega=\frac{2\pi }{86400\,\mathrm{s}}

the Earth’s rotational speed,

Station spatiale helvétique

xa0 We participate in the conception of the future Swiss spatial station (SSS). The SSS has the shape of a cylindrical and hollow wheel. The spacemen live in the wheel in its external surface, their ground is a cylindrical surface of radius R. An artifical gravity is created there by the rotation of the station (constant angular velocity Ω) around its revolution axis. In this exercise, we neglect all effect coming from the proximity of the Earth and we consider that the axis of rotation of the SSS is fix

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Notebooks associés (14)

Digital Simulation of Guitar Feedback in I Feel Fine by The Beatles

I Feel Fine, Digitally[1]¶ This notebook is a little musing inspired by the "internal mechanics" of a very famous audio snippet, namely the guitar sound at the beginning of the song "I Feel Fine", written and recorded by the Beatles in 1964. The historical significance of the record lies in the following claim by John Lennon:

 "I defy anybody to find a record... unless it is some old blues
 record from 1922... that uses feedback that way. So I claim it for
 the Beatles. Before H

Powder X-Ray Diffraction Analysis: Exploring Crystal Structures.

XRay Diffraction[1]¶ The purpose of this notebook is to study the powder XRay diffraction spectra of some systems. When the crystal is hit with an XRay wave, the wave is diffracted only for specific case where the Bragg condition is satisfied for one of the lattice planes in the material. For single crystal diffraction, the condition is satisfied only for specific orientation of the crystal, such that the incident ray has the correct

\theta

value for the plane. In powder XRay data, however, any plane ori

Voice Transformation Techniques Using Digital Signal Processing

A Gallery of Voice Transformers[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

In this notebook we will explore various ways to implement a system that changes the voice of a speaker. Typical applications for these techniques, strictly sorted by plausibility, include international spy missions and prank telephone calls, and devices such as the one displayed here can be easily bought on the web... or in a novelty shop. No description has been provided for t

Investigating the Effect of Phase on Sound Perception

Hearing the phase of a sound[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

In this notebook we will investigate the effect of phase on the perceptual quality of a sound. It is often said that the human ear is commercial-grade audio equipment takes place in the magnitude domain only. In [1]: %matplotlib inline import matplotlib import matplotlib.pyplot as plt import numpy as np import IPython from scipy.io import wavfile In [2]: plt.rcParams["figure.fig

Adaptive Echo Cancellation using LMS Filter

Adaptive Echo Cancellation[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

In this notebook we will use the adaptive LMS filter to estimate the impulse response of a reverberating room. A typical use case is handsfree telephony: since the received signal, amplified and played by the speaker, is picked up by the microphone, we need to eliminate it from the signal that is transmitted back in order to avoid a feedback loop. The signal picked up by the microph

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Notebooks associés (14)

Digital Simulation of Guitar Feedback in I Feel Fine by The Beatles

 "I defy anybody to find a record... unless it is some old blues
 record from 1922... that uses feedback that way. So I claim it for
 the Beatles. Before H

Powder X-Ray Diffraction Analysis: Exploring Crystal Structures.

\theta

value for the plane. In powder XRay data, however, any plane ori

Voice Transformation Techniques Using Digital Signal Processing

A Gallery of Voice Transformers[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

Investigating the Effect of Phase on Sound Perception

Hearing the phase of a sound[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

Adaptive Echo Cancellation using LMS Filter

Adaptive Echo Cancellation[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

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Exercices associés (17)

Cylindre ferromagnétique

An infinite cylinder of ferromagnetic material carries a uniform magnetization

{\bf M}

. What is the current density linked to the surface of the cylinder? Determine the fields

{\bf B}

and

{\bf H}

inside and outside of the cylinder. At the surface of the magnetized cylinder a linked current whose density(current per unit length) is

{\bf K}_b=M\,{\bf \hat{\phi}}

is circulating. The surface of the cylinder is behaving like an infinite coil that carries the same current density. So

{\bf B}={\bf H}=0

Ordre de grandeur

Make some rough estimations (in terms of powers of 10) according to your “feeling” (test for a job interview as “management consultant”...):

How many pencils would you need to draw a straight line along the Earth’s equator ?
How many wedding dresses are sold every year in Italy ?
How many individual hairs are on your head ?
How many water drops are contained in all the oceans of the globe ?
How many CHF 10 banknotes have to be piled up to reach the moon ? Would a space missi

Tapis roulant

At the initial time (tu2004=u20040), the length of the spring is equal to l₀ (i.e. the spring is at rest) and the conveyor starts its function. It drives the mass m at a constant velocity v₀

Question conceptuelle: Coriolis dans votre lavabo

Calculate the order of magnitude of the Coriolis acceleration of the water in your emptying sink. The Coriolis acceleration is expressed with the following equation:

\vec a_{\rm Coriolis}=2\vec{\Omega} \wedge \vec{V} \,

in which Ω⃗ is the Earth’s rotational velocity and V⃗ is the velocity of the water in the sink. We find the following expression for the Coriolis acceleration’s norm:

a_{\rm Coriolis}=2\Omega V \sin\theta \,

with

\Omega=\frac{2\pi }{86400\,\mathrm{s}}

the Earth’s rotational speed,

Station spatiale helvétique

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Sismologie

Chattez avec Graph Search

Adaptive dynamic Q-factor continuous wavelet transform for natural frequency extraction in fault-originated transient signals

The effect of frictional heterogeneities on the seismic cycle: Insights from triaxial experiments

Lithologic Controls on Frictional Behavior Along the Shallow Subduction Interface: Constraints From an Exhumed Accretionary Wedge (McHugh Complex, Alaska)

Adaptive dynamic Q-factor continuous wavelet transform for natural frequency extraction in fault-originated transient signals

The effect of frictional heterogeneities on the seismic cycle: Insights from triaxial experiments

Lithologic Controls on Frictional Behavior Along the Shallow Subduction Interface: Constraints From an Exhumed Accretionary Wedge (McHugh Complex, Alaska)