Nepal earthquake evidence from GNSS data at the Everest Pyramid Lab

2019 ◽  
Vol 481 (1) ◽  
pp. 7-18 ◽  
Author(s):  
G. Poretti ◽  
F. Morsut ◽  
F. Pettenati
Keyword(s):  
Seismic Station ◽  
Integral Function ◽  
Original Position ◽  
Seismic Events ◽  
Accurate Analysis ◽  
Nepal Earthquake ◽  
Gnss Data ◽  
Station Point ◽  
Three Components

AbstractThe permanent GNSS station located at the Everest Pyramid Laboratory of EvK2CNR recorded its position coordinates during the earthquakes at the Gorkha (25 April 2015) and Ghorthali zones (12 May 2015) at an interval of every 30 s. The data recorded over three days prior to and after the earthquakes were analysed and the movement indicated a shifting of the GNSS station point from its original position every 30 s. From an accurate analysis of the coordinates of the station determined using GNSS Bernese software, it is possible to detect the movements of the station during the seismic events.The shifts in the GNSS point were summed to provide an integral function (PIF, Pyramid Integral Function) that can be computed for each of the three components. Comparing them with the displacement record of the GURALP broadband seismic station (IO-EVN) of the OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, OGS, Trieste), located at the Pyramid, it is possible to establish a correlation, particularly with the vertical and north components; the maxima of the PIF coincide with the time of occurrence of the earthquakes.

scholarly journals Repetitive fracturing during spine extrusion at Unzen volcano, Japan

Solid Earth ◽  
2015 ◽  
Vol 6 (4) ◽  
pp. 1277-1293 ◽  
Author(s):  
O. D. Lamb ◽  
S. De Angelis ◽  
K. Umakoshi ◽  
A. J. Hornby ◽  
J. E. Kendrick ◽  
...  
Keyword(s):  
Seismic Data ◽  
Seismic Station ◽  
Physical Models ◽  
Ductile Deformation ◽  
Seismic Events ◽  
Seismic Velocities ◽  
Strain Localisation ◽  
Cyclic Activity ◽  
Geophysical Field ◽  
Unzen Volcano

Abstract. Rhythmic seismicity associated with spine extrusion is a well-documented phenomenon at a number of dome-forming volcanic systems. At Unzen volcano, Japan, a 4-year dome-forming eruption concluded with the emplacement of a spine from October 1994 to February 1995, offering a valuable opportunity to further investigate seismogenic processes at dome-forming volcanoes. Using continuous data recorded at a seismic station located close to the dome, this study explores trends in the seismic activity during the extrusion of the spine. We identify a total of 12 208 volcano-seismic events in the period between October 1994 and February 1995. Hourly event counts indicate cyclic activity with periods of ∼ 40 to ∼ 100 h, attributed to pulsatory ascent defined by strain localisation and faulting at the conduit margins. Waveform correlation revealed two strong clusters (a.k.a. multiplets, families) which are attributed to fracturing along the margins of the shallow, ascending spine. Further analysis indicates variable seismic velocities during the spine extrusion as well as migration of the cluster sources along the spine margins. Our interpretation of the results from seismic data analyses is supported by previously published field and experimental observations, suggesting that the spine was extruded along an inclined conduit with brittle and ductile deformation occurring along the margins. We infer that changes in stress conditions acting on the upper and lower spine margins led to deepening and shallowing of the faulting sources, respectively. We demonstrate that the combination of geophysical, field and experimental evidence can help improve physical models of shallow conduit processes.

scholarly journals High-energy seismic events in Legnica–Głogów Copper District in light of ASG-EUPOS data

2019 ◽  
Vol 107 (1) ◽  
pp. 25-40 ◽  
Author(s):  
Zbigniew Szczerbowski
Keyword(s):  
Rock Mass ◽  
Regional Scale ◽  
Geophysical Methods ◽  
Geodetic Network ◽  
High Energy ◽  
Tectonic Activity ◽  
Baseline Length ◽  
Seismic Events ◽  
Gnss Data ◽  
Mining Tremors

AbstractSeismic events in the area of Poland are related mostly to copper and coal mining, and they are regarded as the most dangerous natural hazard. Although development of geomechanical modelling as the development of geophysical methods determining seismic hazard are evident, low predictability of the time-effect relationship still remains. Geomechanical models as geophysical data analysis highlight the interaction between parts of rock mass or allow to reconstruct the way of rock mass destruction and to understand the processes that take place in the high-energy tremors.However, the association of larger mining tremors with pre-existing geological features has been reported by many investigators; in geomechanical practice, investigations of rock mass condition concentrate on this problem in the local scale. Therefore, the problem of relations between high-energy seismic events in Legnica–Głogów Copper District (LGCD) and regional scale deformations of terrain surface resulting from possible tectonic activity is discussed in this paper. The GNSS data evaluated from the observations of ASG-EUPOS (Active Geodetic Network – EUPOS) stations in the area of LGCD and in the adjacent areas is analysed in this study. Temporal variation of distances between the stations and evaluated on that base so called apparent strain was combined with the occurrence of high-energy tremors. Consequently, after the examination and analysis of occurrences of mining tremors, it is found that high-energy seismic events and periods of strain accumulation evaluated from GPS/GNSS data have temporal relations. Although the seismic events were triggered by mining, nearly all the events with energy E > 108 J occurred in the periods when the analysed stations’ positions demonstrated a decrease in the baseline length.

Quasi-Static Analysis of the Multi-Component Mooring Line for Suction Anchors

2010 ◽  
Author(s):  
Li-zhong Wang ◽  
Zhen Guo ◽  
Feng Yuan
Keyword(s):  
Static Analysis ◽  
Static Model ◽  
Ocean Currents ◽  
Original Position ◽  
Mooring Line ◽  
Soil Resistance ◽  
Two Dimensional ◽  
Accurate Analysis ◽  
Line Type

Multi-component taut mooring line is widely used to connect the floating facility to an embedded suction anchor to provide an effective motion limit. The functions of different components should be evaluated in order to optimize its anchoring performance. This paper presents a novel two-dimensional quasi-static model, which can calculate different combinations of line type, taking into account the effects of ocean currents, soil resistance and elastic elongation of mooring line. Accurate analysis is carried out to predict the responses of multi-component mooring line during pretension and in service. Especially, when the floating facility undergoes a series of motion away from its original position, the effect of vertical offset is studied in detail. Finally, based on the presented model, the functions of different components are throughly investigated and some useful conclusions are drawn.

scholarly journals Evaluation of the depth of the Pantanal sedimentar basin based on seismic events

2021 ◽  
Vol 10 (9) ◽  
pp. e57710918243
Author(s):  
Amanda Letícia Abegg da Silveira ◽  
Gustavo Marques e Amorim ◽  
Dhonatan Diego Pessi ◽  
Normandes Matos da Silva ◽  
Camila Leonardo Mioto ◽  
...  
Keyword(s):  
Seismic Waves ◽  
Sedimentary Basin ◽  
Seismic Station ◽  
Seismic Events ◽  
Mato Grosso ◽  
Loss Of Information ◽  
Northern Portion

The main objective of this study is qualify the seismic activities captured at the Santo Antônio do Leverger seismic station (SALV), state of Mato Grosso, Brazil. The choice of this station was due to its location in the northern portion of the Pantanal Sedimentary Basin, considered historically as one of the seismogenic regions of Brazil. The methodology involved downloading the files through the poet.py script, where the events were identified, selected and stored within 440 km from the SALV station. Once confirmed, filtrations were applied using the Butterworth method. This method minimizes the loss of information recorded by events that have occurred. Thus, most events indicate disagreement with the applied filters, demonstrating that there is a structure that influences the propagation of the wave, changing its original speed and frequency. The triggering method was applied to the behavior of seismic waves that crossed the sedimentary interval of the Pantanal Basin. The results were plotted on maps, overlaid in the form of sub-regions of the Pantanal using the QGIS geoprocessing software, in which the geological contacts were determined. Thus, it was possible to observe that each sub-region presents a different profile for each event, with sub-regions that tend to increase the signal's acceleration, maintain it or slow it down.

scholarly journals Palaeoseismicity in the Siwaliks: occurrence of major seismic events in the Himalayas of west Nepal

1998 ◽  
Vol 18 ◽  
Author(s):  
Georges H. Mascle ◽  
Edouard Chalaron ◽  
A. P. Gajurel ◽  
Pascale Leturmy ◽  
Jean Louis Mugnier
Keyword(s):  
Foreland Basin ◽  
Seismic Events ◽  
Thrust Belt ◽  
Earthquake Intensity ◽  
Active Deformation ◽  
Nepal Earthquake ◽  
The Himalaya

The Siwaliks represent both the Neogene-Quaternary foreland thrust belt of the Himalaya and the sedimentary series of fluvial origin that have been deposited in a flexural foreland basin near the mobile front of the Himalayan range and have been successively incorporated by thrusting to the structural edifice. The still active deformation of the Siwalik prism occurs through both the seismic and aseismic regime. Structures of syn-sedimentary liquefaction are observed in the Upper Siwaliks of the well dated Surai Khola section of western Nepal. Two particularly thick liquefied layers occur near the base of the Dobata Formation of around 4.1 Ma in age and are also observed in the Babai Khola section about 120 km west of the Surai Khola. These data are compared with the extension of liquefaction induced by modem earthquakes in the area (mainly the 1934 Bihar-Nepal earthquake) and plotted on two graphs: 1- maximum epicentre distance from liquefied sites versus magnitude of earthquake; 2- thickness of liquefied layers versus earthquake intensity. All the results agree with the occurrence of major paleoearthquakes in the area.

scholarly journals Fast estimation of earthquake arrival azimuth using a single seismological station and machine learning techniques

2019 ◽  
Vol 23 (2) ◽  
pp. 103-109 ◽  
Author(s):  
Luis Hernán Ochoa Gutierrez ◽  
Carlos Alberto Vargas Jiménez ◽  
Luis Fernando Niño Vásquez
Keyword(s):  
Machine Learning ◽  
Seismic Station ◽  
Machine Learning Techniques ◽  
Time Signal ◽  
Support Vector ◽  
Seismic Events ◽  
Frequency Noise ◽  
Learning Techniques ◽  
Vector Machines ◽  
Time Signals

The objective of this research is to apply a new approach to estimate arrival azimuth of seismic events using seismological records of the “El Rosal” station, near to the city of Bogota – Colombia, by applying support vector machines (SVMs). The algorithm was trained with time signal descriptors of 863 seismic events acquired from January 1998 to October 2008; considering only events with magnitude ≥ 2 ML.  The earthquake signals were filtered in order to remove diverse kind of low and high frequency noise not related to such events. During training stages of SVMs, several combinations of kernel function exponent and complexity factor were applied to time signals of 5, 10 and 15 seconds along with earthquake magnitudes of 2.0, 2.5, 3.0 and 3.5 ML. The best classification of SVMs was obtained using time signals of 5 seconds and earthquake magnitudes greater than 3.0 ML with kernel exponent of 10 and complexity factor of 2, showing accuracy of 45.4 degrees. This research is an improvement of previous works related to earthquake arrival azimuth determination from data of one single seismic station employing machine learning techniques. 

scholarly journals Cyclic fracturing during spine extrusion at Unzen volcano, Japan

2015 ◽  
Vol 7 (3) ◽  
pp. 2109-2149 ◽  
Author(s):  
O. D. Lamb ◽  
S. De Angelis ◽  
K. Umakoshi ◽  
A. J. Hornby ◽  
J. E. Kendrick ◽  
...  
Keyword(s):  
Seismic Data ◽  
Seismic Station ◽  
Ductile Failure ◽  
Physical Models ◽  
Seismic Events ◽  
Seismic Velocities ◽  
Strain Localisation ◽  
Cyclic Activity ◽  
Geophysical Field ◽  
Unzen Volcano

Abstract. Rhythmic seismicity associated with spine extrusion is a well-documented phenomenon at a number of dome-forming volcanic systems. At Unzen volcano, Japan, a four year dome-forming eruption concluded with the emplacement of a spine from October 1994 to February 1995, offering a valuable opportunity to further investigate seismogenic processes at dome-forming volcanoes. Using continuous data recorded at a seismic station located close to the dome, this study explores trends in the seismic activity during the extrusion of the spine. We identify a total of 12 208 seismic events in the period between October 1994 and February 1995. Hourly event counts indicate cyclic activity with periods of ~ 40 to ~ 100 h, attributed to pulsatory ascent defined by strain localisation and faulting at the conduit margins. Waveform correlation revealed two strong clusters (a.k.a. multiplets, families) attributed to fracturing along the margins of the shallow, ascending plug. Further analysis indicates variable seismic velocities during spine extrusion, as well as migration of the cluster sources along the spine margins. Our interpretation of the results from seismic data analyses is supported by field and experimental observations, suggesting that the spine was extruded along an inclined conduit with brittle and ductile failure occurring along the margins. We infer that changes in stress conditions acting on the upper and lower spine margins led to deepening and shallowing of the faulting source, respectively. We demonstrate that the combination of geophysical, field and experimental evidence can help improve physical models of shallow conduit processes.

The Jovian ring

1984 ◽  
Vol 75 ◽  
pp. 203-209
Author(s):  
Joseph A. Burns
Keyword(s):  
Equatorial Plane ◽  
Charged Particles ◽  
Dynamical Evolution ◽  
Main Band ◽  
Small Grains ◽  
Three Components

ABSTRACTLying in Jupiter's equatorial plane is a diaphanous ring having little substructure within its three components (main band, faint disk, and halo). Micron-sized grains account for much of the visible ring, but particles of centimeter sizes and larger must also be present to absorb charged particles. Since dynamical evolution times and survival life times are quite short (≲102-3yr) for small grains, the Jovian ring is being continually replenished; probably most of the visible ring is generated by micrometeoroids colliding into unseen parent bodies that reside in the main band.

Point-Cathode Electron Gun Using Electron-Beam Bombardment for Cathode Tip Heating

1990 ◽  
Vol 48 (1) ◽  
pp. 198-199
Author(s):  
Ryo Iiyoshi ◽  
Susumu Maruse ◽  
Hideo Takematsu
Keyword(s):  
Electron Beam ◽  
Tungsten Wire ◽  
Local Heating ◽  
Electron Gun ◽  
Original Position ◽  
Beam Power ◽  
Radius Of Curvature ◽  
High Brightness ◽  
Beam Focusing ◽  
Time Operation

Point cathode electron gun with high brightness and long cathode life has been developed. In this gun, a straightened tungsten wire is used as the point cathode, and the tip is locally heated to higher temperatures by electron beam bombardment. The high brightness operation and some findings on the local heating are presented.Gun construction is shown in Fig.l. Small heater assembly (annular electron gun: 5 keV, 1 mA) is set inside the Wehnelt electrode. The heater provides a disk-shaped bombarding electron beam focusing onto the cathode tip. The cathode is the tungsten wire of 0.1 mm in diameter. The tip temperature is raised to the melting point (3,650 K) at the beam power of 5 W, without any serious problem of secondary electrons for the gun operation. Figure 2 shows the cathode after a long time operation at high temperatures, or high brightnesses. Evaporation occurs at the tip, and the tip part retains a conical shape. The cathode can be used for a long period of time. The tip apex keeps the radius of curvature of 0.4 μm at 3,000 K and 0.3 μm at 3,200 K. The gun provides the stable beam up to the brightness of 6.4×106 A/cm2sr (3,150 K) at the accelerating voltage of 50 kV. At 3.4×l06 A/cm2sr (3,040 K), the tip recedes at a slow rate (26 μm/h), so that the effect can be offset by adjusting the Wehnelt bias voltage. The tip temperature is decreased as the tip moves out from the original position, but it can be kept at constant by increasing the bombarding beam power. This way of operation is possible for 10 h. A stepwise movement of the cathode is enough for the subsequent operation. Higher brightness operations with the rapid receding rates of the tip may be improved by a continuous movement of the wire cathode during the operations. Figure 3 shows the relation between the beam brightness, the tip receding rate by evaporation (αis the half-angle of the tip cone), and the cathode life per unit length, as a function of the cathode temperature. The working life of the point cathode is greatly improved by the local heating.

Left Ventricular Hypertrophy

2014 ◽  
Vol 19 (2) ◽  
pp. 11-15
Author(s):  
Steven L. Demeter
Keyword(s):  
Risk Factors ◽  
Left Ventricular Hypertrophy ◽  
Ventricular Hypertrophy ◽  
Left Ventricular Mass Index ◽  
Medical Science ◽  
Careful Analysis ◽  
Left Ventricular ◽  
Hypertensive Disease ◽  
Accurate Analysis ◽  
Clear Explanation

Abstract The fourth, fifth, and sixth editions of the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) use left ventricular hypertrophy (LVH) as a variable to determine impairment caused by hypertensive disease. The issue of LVH, as assessed echocardiographically, is a prime example of medical science being at odds with legal jurisprudence. Some legislatures have allowed any cause of LVH in a hypertensive individual to be an allowed manifestation of hypertensive changes. This situation has arisen because a physician can never say that no component of LVH was not caused by the hypertension, even in an individual with a cardiomyopathy or valvular disorder. This article recommends that evaluators consider three points: if the cause of the LVH is hypertension, is the examinee at maximum medical improvement; is the LVH caused by hypertension or another factor; and, if apportionment is allowed, then a careful analysis of the risk factors for other disorders associated with LVH is necessary. The left ventricular mass index should be present in the echocardiogram report and can guide the interpretation of the alleged LVH; if not present, it should be requested because it facilitates a more accurate analysis. Further, if the cause of the LVH is more likely independent of the hypertension, then careful reasoning and an explanation should be included in the impairment report. If hypertension is only a partial cause, a reasoned analysis and clear explanation of the apportionment are required.

Sign in / Sign up

Export Citation Format

Share Document