scholarly journals A physical model of the high‐frequency seismic signal generated by debris flows

2019 ◽  
Vol 44 (13) ◽  
pp. 2529-2543 ◽  
Author(s):  
Maxime Farin ◽  
Victor C. Tsai ◽  
Michael P. Lamb ◽  
Kate E. Allstadt
Keyword(s):  
Physical Model ◽  
High Frequency ◽  
Debris Flows ◽  
Seismic Signal

Analyzing bulk flow characteristics of debris flows using their high frequency seismic signature

2021 ◽  
Author(s):  
Zhen Zhang ◽  
Fabian Walter ◽  
Brian W. McArdell ◽  
Tjalling Haas ◽  
Michaela Wenner ◽  
...  
Keyword(s):  
High Frequency ◽  
Debris Flows ◽  
Flow Characteristics ◽  
Bulk Flow ◽  
Seismic Signature

scholarly journals Analysis of the ground vibration generated by debris flows and other torrential processes at the Rebaixader monitoring site (Central Pyrenees, Spain)

2014 ◽  
Vol 14 (4) ◽  
pp. 929-943 ◽  
Author(s):  
C. Abancó ◽  
M. Hürlimann ◽  
J. Moya
Keyword(s):  
High Frequency ◽  
Debris Flows ◽  
Low Frequency ◽  
Ground Vibration ◽  
Monitoring Site ◽  
Velocity Signal ◽  
Vibration Sensors ◽  
Definition Of ◽  
Flow Detection ◽  
Central Pyrenees

Abstract. Monitoring of debris flows using ground vibration sensors has increased in the last two decades. However, the correct interpretation of the signals still presents ambiguity. In the Rebaixader monitoring site (Central Pyrenees, Spain) two different ground vibration stations are installed. At the first station the ground velocity signal is transformed into an impulses-per-second signal (low frequency, 1 Hz). The analysis of the data recorded at this station show that the shape of the impulses signal is one of the key parameters to describe the evolution of the event. At the second station the ground velocity signal is directly recorded at high frequency (250 Hz). The results achieved at this station show that the differences in time series and spectral analysis are helpful to describe the temporal evolution of the events. In addition, some general outcomes were obtained: the attenuation of the signal with the distance has been identified as linear to exponential; and the assembly of the geophones to the terrain has an important effect on the amplification of the signal. All these results highlight that the definition of ground vibration thresholds for debris-flow detection or warning purposes is a difficult task; and that influence of site-specific conditions is notable.

Daytime and nighttime turbulence on Mars monitored by InSight

2020 ◽  
Author(s):  
Aymeric Spiga ◽  
Naomi Murdoch ◽  
Don Banfield ◽  
Ralph Lorenz ◽  
Claire Newman ◽  
...  
Keyword(s):  
Gravity Waves ◽  
High Frequency ◽  
Seismic Signal ◽  
Atmospheric Science ◽  
Large Eddy Simulations ◽  
Dust Devil ◽  
Large Eddy ◽  
The Many ◽  
Convective Vortices

<p>The InSight instrumentation for atmospheric science combines high frequency, high accuracy and continuity. This makes InSight a mission particularly suitable for studies of the variability in the Planetary Boundary Layer (PBL) of Mars -- all the more since this topic is of direct interest for quake detectability given that turbulence is the main contributor to atmosphere-induced seismic signal. For the strong daytime buoyancy-driven PBL convection, InSight significantly extends the statistics of dust-devil-like convective vortices and turbulent wind gustiness, both of which are of strong interest for aeolian science. For the moderate nighttime shear-induced PBL convection, InSight enables to explore phenomena and variability left unexplored by previous in-situ measurements on Mars. In both daytime and nighttime environments, how the gravity waves and infrasound signals discovered by InSight are being guided within the PBL is also a central topic to InSight's atmospheric investigations, with the tantalizing possibility to identify possible sources for those phenomena. InSight has been operating at the surface of Mars since 18 months, thus the seasonal evolution of the many phenomena occurring in the PBL will be an emphasis of this report. Comparisons with turbulence-resolving modeling such as Large-Eddy Simulations will be also discussed.</p>

scholarly journals Landslides distribution at tributaries with different evolution stages in Jiangjia Gully, southwestern China

2019 ◽  
Author(s):  
Xia Fei Tian ◽  
Yong Li ◽  
Quan Yan Tian ◽  
Feng Huan Su
Keyword(s):  
High Frequency ◽  
Debris Flows ◽  
Satellite Image ◽  
Flow Regimes ◽  
Southwestern China ◽  
Grid Cells ◽  
Jiangjia Gully ◽  
Material Sources ◽  
Main Material

Abstract. Jiangjia Gully (JJG) is known for its high frequency and variety of debris flows, especially the intermittent surges of various flow regimes and materials. Observation indicates that the surges come from various tributaries with different landslides activities. In this study, 81 tributaries of JJG are taken from DEM with 10 m grid cells, and the hypsometric curves are used to characterize their evolution stages; five stages are identified by the evolution index (EI, the integral of the hypsometric curves) and most tributaries are in relative youth stage with EI between 0.5 and 0.6. Then 908 landslides are interpreted from Quickbird satellite image of 0.61 m resolution, and it is found that LD (LD = landslides number in a tributary/the tributary area) increases exponentially with EI, while LAp (LAp = landslides area in a tributary/the tributary area) fluctuates with EI, meaning that landslides are inclined to occur in tributaries with EI between 0.5 and 0.6, and thus these tributaries are the main material sources supplying for debris flows.

Wall motion in expiratory flow limitation: choke and flutter

1985 ◽  
Vol 59 (4) ◽  
pp. 1304-1312 ◽  
Author(s):  
P. M. Webster ◽  
R. P. Sawatzky ◽  
V. Hoffstein ◽  
R. Leblanc ◽  
M. J. Hinchey ◽  
...  
Keyword(s):  
Physical Model ◽  
High Frequency ◽  
Pure Tone ◽  
Wave Speed ◽  
Wall Motion ◽  
Flow Limitation ◽  
Two Dimensional ◽  
Potential Mechanism ◽  
Expiratory Flow Limitation ◽  
Supercritical Flow

Limitation of expiratory airflow from mammalian airways is currently understood to be due to choking at wave speed (S. V. Dawson and E. A. Elliott. J. Appl. Physiol. 43: 498–515, 1977). A critical weakness of the theory is the lack of a mechanism for the dissipation of energy when effort exceeds that needed for maximal flow. We have observed substantial wall motion with flow limitation in a physical model of a trachea. Therefore we have examined a simple two-dimensional mathematical model, designed to approximate the behavior of the physical model of the trachea, to try to identify a relationship between flow limitation and wall oscillation. The model matches wave-speed predictions when only long waves are considered. The model predicts that aerodynamic flutter will occur in the zone of supercritical flow described in wave-speed theory. Aerodynamic flutter in the zone of supercritical flow provides a potential mechanism for the energy dissipation necessary for transition from supercritical to subcritical flow and explains the high-frequency pure tone heard with flow limitation.

scholarly journals Insights from the particle impact model into the high frequency seismic signature of debris flows

2020 ◽  
Author(s):  
Zhen Zhang ◽  
Fabian Walter ◽  
Brian W. McArdell ◽  
Michaela Wenner ◽  
Małgorzata Chmiel ◽  
...  
Keyword(s):  
High Frequency ◽  
Debris Flows ◽  
Particle Impact ◽  
Impact Model ◽  
Seismic Signature

Burial Process of a Seismic Station by Moving Dunes in Tarim Basin

2020 ◽  
Vol 91 (5) ◽  
pp. 2936-2941
Author(s):  
Xiaofeng Liang ◽  
Sicheng Zuo ◽  
Shilin Li ◽  
Yongge Feng
Keyword(s):  
High Frequency ◽  
Noise Level ◽  
Seismic Station ◽  
Low Frequency ◽  
Seismic Signal ◽  
Frequency Noise ◽  
Temperature Record ◽  
Environment Change ◽  
Broadband Seismometer ◽  
High Frequency Noise

Abstract A temporary seismometer vault was buried by a moving sand dune in the Taklimakan Desert at northwestern China in October 2019. The dune gradually covered the solar panel and the power supply to the seismic station was subsequently cut off. Here, we show that the burial process can be diagnosed according to the temperature record from the thermometer in the data-logger, an ultra-low-frequency seismic signal, and the change of high-frequency noise level from the continuous seismograms recorded by the broadband seismometer. The ultra-low-frequency seismic signal reflects the thermoelastic effect of the suspension spring in the seismometer corresponding to the temperature gradient in the sensor vault. At the same time, the variation of high-frequency noise level correlates well with the temperature profile and the ultra-low-frequency seismic signal, indicating the ground wind intensity. The peak frequency shifts and their different responses on three-component waveforms for the high-frequency noise might reflect the distance from the moving dunes to the station and their moving directions. This observation shows a potential usage of continuous seismograms to study rapid environment change around a temporary seismic station.

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