Extracting coherent coda arrivals from cross-correlations of long period seismic waves during the Mount St. Helens 2004 eruption

2006 ◽  
Vol 33 (6) ◽  
Author(s):  
Karim G. Sabra ◽  
Philippe Roux ◽  
Peter Gerstoft ◽  
W. A. Kuperman ◽  
Michael C. Fehler
Keyword(s):  
Seismic Waves ◽  
Long Period ◽  
Cross Correlations ◽  
Mount St Helens

Isolation Performance of Intelligent Seismic Isolation System Using Air Bearing

2009 ◽  
Author(s):  
Satoshi Fujita ◽  
Keisuke Minagawa ◽  
Mitsuru Miyazaki ◽  
Go Tanaka ◽  
Toshio Omi ◽  
...  
Keyword(s):  
Seismic Isolation ◽  
Seismic Waves ◽  
Three Dimensional ◽  
Vertical Motion ◽  
Air Bearings ◽  
Natural Period ◽  
Isolation System ◽  
Vertical Excitation ◽  
Long Period ◽  
Isolation Performance

This paper describes three-dimensional isolation performance of seismic isolation system using air bearings. Long period seismic waves having predominant period of from a few seconds to a few ten seconds have recently been observed in various earthquakes. Also resonances of high-rise buildings and sloshing of petroleum tanks in consequence of long period seismic waves have been reported. Therefore the isolation systems having very long natural period or no natural period are required. In a previous paper [1], we proposed an isolation system having no natural period by using air bearings. Additionally we have already reported an introduction of the system, and have investigated horizontal motion during earthquake in the previous paper. It was confirmed by horizontal vibration experiment and simulation in the previous paper that the proposed system had good performance of isolation. However vertical motion should be investigated, because vertical motion varies horizontal frictional force. Therefore this paper describes investigation regarding vertical motion of the proposed system by experiment. At first, a vertical excitation test of the system is carried out so as to investigate vertical dynamic property. Then a three-dimensional vibration test using seismic waves is carried out so as to investigate performance of isolation against three-dimensional seismic waves.

Fundamental Study on the Super-Long-Period Active Isolation System

2004 ◽  
Author(s):  
Keisuke Minagawa ◽  
Satoshi Fujita
Keyword(s):  
Control System ◽  
Seismic Isolation ◽  
Seismic Waves ◽  
Model Matching ◽  
Fundamental Study ◽  
Natural Period ◽  
Isolation System ◽  
Long Period ◽  
Rubber Bearings ◽  
Classical Control

Since the Hanshin-Awaji Earthquake Disaster, the number of isolated structures has been greatly increased. The natural period of the isolation system is designed around 3 seconds, because predominate period of observed seismic waves is usually 0.1 to 1 second. However, relatively long period seismic waves have been observed in various earthquakes, and the resonance of long-period structures, such as high-rise buildings, during earthquakes have been reported at the same time. Therefore the natural period needs to be extended. When extending the natural period of the isolated structure using rubber bearings, its stiffness needs to be reduced. It is more difficult to extend the natural period of the isolation system than the conventional system because of its buckling problem. Therefore we propose a super-long-period active seismic isolation system as a new method for extending the natural period of the isolated structure. This system consists of rubber bearings and actuators. In this study, we designed a control system by using the model-matching-method. This is one of the classical control system design methods. We investigated the isolation performance by numerical analysis. In addition, we selected the optimal variables of transfer function using genetic algorithm.

scholarly journals The source of infrasound associated with long‐period events at Mount St. Helens

2009 ◽  
Vol 114 (B4) ◽  
Author(s):  
Robin S. Matoza ◽  
Milton A. Garcés ◽  
Bernard A. Chouet ◽  
Luca D'Auria ◽  
Michael A. H. Hedlin ◽  
...  
Keyword(s):  
Long Period ◽  
Mount St Helens

scholarly journals GEODYNAMICS

GEODYNAMICS ◽  
2011 ◽  
Vol 2(11)2011 (2(11)) ◽  
pp. 344-346
Author(s):  
V.P. Shljahovyj ◽  
◽  
O. Kendzera ◽  
V.V. Shljahovyj ◽  
◽  
...  
Keyword(s):  
Seismic Waves ◽  
Seismic Signal ◽  
Long Period ◽  
Gravitational Contribution

Possibility of use of tidal devices for record of seismic waves from earthquakes and other geodynamic events is studied. It is investigated the inertial and gravitational contribution of seismic signal to pendular seismometers and tidal devices (seismotiltmeter and gravimeter). These are identical devices and differ stability of blocks and in filtration parameters. Tidal devices are more sensitive in over-long-period area where the gravitational contribution is more. It is given examples of record of seismic fluctuations by tidal devices at some earthquakes

Research and Development of Intelligent Seismic Isolation System Using Air Bearing

2008 ◽  
Author(s):  
Satoshi Fujita ◽  
Keisuke Minagawa ◽  
Mitsuru Miyazaki ◽  
Go Tanaka ◽  
Osamu Takahashi
Keyword(s):  
Friction Coefficient ◽  
Seismic Wave ◽  
Seismic Isolation ◽  
Seismic Waves ◽  
Air Bearing ◽  
Natural Period ◽  
Isolation System ◽  
Long Period ◽  
Isolation Device ◽  
Isolation Performance

This study aims at research and development of the intelligent seismic isolation system using air bearings as isolation device and Earthquake Early Warning (EEW) as trigger of isolation system. In October 2007, EEW was started providing to resident of Japan. The EEW system expects earthquake intensity and arrival time at particular place by analysis of seismic wave that was observed near the earthquake center. Therefore social and technical application of the system is strongly expected for suppression of disaster scale. On the other hand, long period seismic waves having predominant period of from a few seconds to a few ten seconds have recently been observed in various earthquakes. Also resonances of high-rise buildings and sloshing of petroleum tanks in consequence of long period seismic waves have been reported. In metropolises of Japan such as Tokyo, Osaka and Nagoya, it is expected that long period seismic waves are excited in large earthquakes because these are located on sedimentary layers. Therefore the isolation system having very long natural period or no natural period is required. In this study, we propose an isolation system having no natural period by using air bearing as isolation device. Air bearing is a bearing that can reduce contact friction between floor and the bearing by thin air film produced by compressed air. In general, the air bearing is used as heavy machinery moving equipment. The approximate friction coefficient is 0.0005 to 0.001, so that the system using air bearing almost isolates seismic wave. In addition, the EEW is applied as trigger of isolation. The EEW is applied for turning gas and electrical heater off, too. P-wave sensor is also equipped and it can operate as trigger in case of near-field earthquake or when EEW system could not work properly. Furthermore, steel plate equipped at the bottom of the air bearing can operate as friction bearing when air bearing does not work. In this paper, we describe results of earthquake response analysis of the intelligent isolation system using air bearing. From results of the analysis, it was confirmed that response acceleration depends on friction coefficient only, and the system has good isolation performance not only against typical seismic wave, such as El Centro wave, but also against long period seismic wave. However residual displacement remains after seismic input stopped. Additionally, experimental test was executed so as to investigate basic performance of isolation. As a result, it was confirmed that the isolation system has good isolation performance.

Parallel Computing Traveling Wave Effect on the Seismic Response of 3D Valley Topography Site under Long-Period Seismic Excitation

2010 ◽  
Vol 163-167 ◽  
pp. 3904-3909
Author(s):  
Wei Zhang ◽  
Min Wei Zhu ◽  
Tao Tao Shan
Keyword(s):  
Parallel Computation ◽  
Traveling Wave ◽  
Seismic Waves ◽  
Three Dimensional ◽  
Vertical Acceleration ◽  
Wave Excitation ◽  
Acceleration Response ◽  
Horizontal Acceleration ◽  
Long Period ◽  
Response Increase

In this paper, three typical bedrock long-period seismic waves and two commonly used waves were selected for three dimensional seismic responses parallel computation of a valley topography site under uniform excitation and traveling wave excitation. The equivalent-linear analysis method was used in simulation of soil’s non-linear properties. Computation results showed that horizontal acceleration response increase and vertical acceleration response decrease under long-period seismic wave excitation compared with those under commonly used waves excitation. When considering wave traveling effect, the horizontal acceleration response decrease and the vertical acceleration response increase. The conclusions are useful for relevant engineering projects. Parallel computation was also performed to raise computational efficiency.

Long-Period Seismic Waves from Nuclear Explosions in Various Environments

Science ◽  
1960 ◽  
Vol 131 (3416) ◽  
pp. 1804-1805 ◽  
Author(s):  
Jack Oliver ◽  
Paul Pomeroy ◽  
Maurice Ewing
Keyword(s):  
Solid Earth ◽  
Seismic Waves ◽  
Upper Atmosphere ◽  
Nuclear Explosions ◽  
Long Period

Large nuclear explosions in the solid earth, the hydrosphere, and the lower and upper atmosphere have generated seismic waves of periods greater than about 5 seconds which have been detected at great distances from the source.

Sign in / Sign up

Export Citation Format

Share Document