Locating rockfalls using inter-station ratios of seismic energy at Dolomieu crater, Piton de la Fournaise volcano

AbstractThe knowledge of the dynamic of the Campi Flegrei calderic system is a primary goal to mitigate the volcanic risk in one of the most densely populated volcanic areas in the world. From 1950 to 1990 Campi Flegrei suffered three bradyseismic crises with a total uplift of 4.3 m. After 20 years of subsidence, the uplift started again in 2005 accompained by a low increment of the seismicity rate. In 2012 an increment in the seismic energy release and a variation in the gas composition of the fumaroles of Solfatara (in the central area of the caldera) were recorded. Since then, a slow and progressive increase in phenomena continued until today. We analyze the INGV - Osservatorio Vesuviano seismic catalogue of Campi Flegrei from 2000 to 2020 in order to look for any variation in the seismic parameters and compare them with geochemical monitored ones. A remarkable correlation between independent variables of earthquake cumulative number, CO/CO2 values and vertical ground deformation reveals a likely common origin. Moreover the correlation between all the variables here analysed enlightens that the same origin can cause the temporal behavior of all these variables. We interpret the seismological, geochemical and geodetic observable in terms of the injection of magmatic fluids into the hydrothermal system or its pressurization.

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Seismic Energy Release from Intra-Basin Sources along the Dead Sea Transform and Its Influence on Regional Ground Motions

Bulletin of the Seismological Society of America ◽

10.1785/0120200215 ◽

2020 ◽

Author(s):

Roey Shimony ◽

Zohar Gvirtzman ◽

Michael Tsesarsky

Keyword(s):

Ground Motions ◽

Seismic Energy ◽

Sedimentary Basins ◽

Seismic Wave Propagation ◽

Dead Sea ◽

Strike Slip ◽

Dead Sea Transform ◽

Bay Area ◽

The Dead ◽

Surrounding Areas

ABSTRACT The Dead Sea Transform (DST) dominates the seismicity of Israel and neighboring countries. Whereas the instrumental catalog of Israel (1986–2017) contains mainly M<5 events, the preinstrumental catalog lists 14 M 7 or stronger events on the DST, during the past two millennia. Global Positioning System measurements show that the slip deficit in northern Israel today is equivalent to M>7 earthquake. This situation highlights the possibility that a strong earthquake may strike north Israel in the near future, raising the importance of ground-motion prediction. Deep and narrow strike-slip basins accompany the DST. Here, we study ground motions produced by intrabasin seismic sources, to understand the basin effect on regional ground motions. We model seismic-wave propagation in 3D, focusing on scenarios of Mw 6 earthquakes, rupturing different active branches of the DST. The geological model includes the major structures in northern Israel: the strike-slip basins along the DST, the sedimentary basins accompanying the Carmel fault zone, and the densely populated and industrialized Zevulun Valley (Haifa Bay area). We show that regional ground motions are determined by source–path coupling effects in the strike-slip basins, before waves propagate into the surrounding areas. In particular, ground motions are determined by the location of the rupture nucleation within the basin, the near-rupture lithology, and the basin’s local structure. When the rupture is located in the crystalline basement or along material bridges connecting opposite sides of the fault, ground motions behave predictably, decaying due to geometrical spreading and locally amplified atop sedimentary basins. By contrast, if rupture nucleates or propagates into shallow sedimentary units of the DST strike-slip basins, ground motions are amplified within, before propagating outside. Repeated reflections from the basin walls result in a “resonant chamber” effect, leading to stronger regional ground motions with prolonged durations.

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Evaluation of Seismic Energy Absorption with Various Hysteretic Models by 2D and 3D Nonlinear Time History Analyses

Structural Engineering International ◽

10.1080/10168664.2018.1545521 ◽

2019 ◽

Vol 30 (1) ◽

pp. 94-101

Author(s):

Somayyeh Karimiyan

Keyword(s):

Energy Absorption ◽

Time History ◽

Seismic Energy ◽

Nonlinear Time History Analyses ◽

Nonlinear Time History ◽

2D And 3D

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The Influence of Surface Topography on the Weak Ground Shaking in Kathmandu Valley during the 2015 Gorkha Earthquake, Nepal

Sensors ◽

10.3390/s20030678 ◽

2020 ◽

Vol 20 (3) ◽

pp. 678

Author(s):

Mark van der Meijde ◽

Md Ashrafuzzaman ◽

Norman Kerle ◽

Saad Khan ◽

Harald van der Werff

Keyword(s):

Numerical Simulations ◽

Surface Topography ◽

Seismic Energy ◽

Spectral Element ◽

Kathmandu Valley ◽

Ground Displacement ◽

Gorkha Earthquake ◽

Ground Shaking ◽

Earthquake Scenarios ◽

2015 Gorkha Earthquake

It remains elusive why there was only weak and limited ground shaking in Kathmandu valley during the 25 April 2015 Mw 7.8 Gorkha, Nepal, earthquake. Our spectral element numerical simulations show that, during this earthquake, surface topography restricted the propagation of seismic energy into the valley. The mountains diverted the incoming seismic wave mostly to the eastern and western margins of the valley. As a result, we find de-amplification of peak ground displacement in most of the valley interior. Modeling of alternative earthquake scenarios of the same magnitude occurring at different locations shows that these will affect the Kathmandu valley much more strongly, up to 2–3 times more, than the 2015 Gorkha earthquake did. This indicates that surface topography contributed to the reduced seismic shaking for this specific earthquake and lessened the earthquake impact within the valley.

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Experimental Research and Finite Element Analysis on Behavior of Steel Frame with Semi-Rigid Connections

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.168-170.553 ◽

2010 ◽

Vol 168-170 ◽

pp. 553-558

Author(s):

Feng Xia Li ◽

Bu Xin

Keyword(s):

Architectural Design ◽

Plastic Hinge ◽

Steel Frames ◽

Seismic Energy ◽

Internal Force ◽

Steel Frame ◽

Frame Structure ◽

Element Analysis ◽

Rigid Deformation ◽

Steel Frame Structure

Most steel beam-column connections actually show semi-rigid deformation behavior that can contribute substantially to overall displacements of the structure and to the distribution of member forces. Steel frame structure with semi-rigid connections are becoming more and more popular due to their many advantages such as the better satisfaction with the flexible architectural design, low inclusive cost and environmental protect as well. So it is very necessary that studying the behavior of those steel frame under cyclic reversal loading. On the basics of connections experiments the experiment research on the lateral resistance system of steel frame structure has been completed. Two one-second scale, one-bay, two-story steel frames with semi-rigid connections under cyclic reversal loading. The seismic behavior of the steel frames with semi-rigid connections, including the failure pattern, occurrence order of plastic hinge, hysteretic property and energy dissipation, etc, was investigated in this paper. Some conclusions were obtained that by employing top-mounted and two web angles connections, the higher distortion occurred in the frames, and the internal force distributing of beams and columns was changed, and the ductility and the absorbs seismic energy capability of steel frames can be improved effectively.

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Structural interpretation using refraction velocities from marine seismic surveys

Geophysics ◽

10.1190/1.1442026 ◽

1986 ◽

Vol 51 (1) ◽

pp. 12-19 ◽

Cited By ~ 3

Author(s):

James F. Mitchell ◽

Richard J. Bolander

Keyword(s):

Sedimentary Rock ◽

Seismic Energy ◽

Seismic Survey ◽

Subsurface Structure ◽

Seismic Reflection Data ◽

Near Surface ◽

Reflection Data ◽

Wide Range ◽

Streamer Length ◽

Set Up

Subsurface structure can be mapped using refraction information from marine multichannel seismic data. The method uses velocities and thicknesses of shallow sedimentary rock layers computed from refraction first arrivals recorded along the streamer. A two‐step exploration scheme is described which can be set up on a personal computer and used routinely in any office. It is straightforward and requires only a basic understanding of refraction principles. Two case histories from offshore Peru exploration demonstrate the scheme. The basic scheme is: step (1) shallow sedimentary rock velocities are computed and mapped over an area. Step (2) structure is interpreted from the contoured velocity patterns. Structural highs, for instance, exhibit relatively high velocities, “retained” by buried, compacted, sedimentary rocks that are uplifted to the near‐surface. This method requires that subsurface structure be relatively shallow because the refracted waves probe to depths of one hundred to over one thousand meters, depending upon the seismic energy source, streamer length, and the subsurface velocity distribution. With this one requirement met, we used the refraction method over a wide range of sedimentary rock velocities, water depths, and seismic survey types. The method is particularly valuable because it works well in areas with poor seismic reflection data.

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