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Sensors to Ensure the Sustainability of Structures
Published in P. C. Thomas, Vishal John Mathai, Geevarghese Titus, Emerging Technologies for Sustainability, 2020
J. Deepthi, C. S. Belarmin Xavier
Seismographs measures the movement of the earth through a ground motion detection sensor, called a seismometer, coupled with a recording system. Seismometers are sensitive to up down motions of the earth. Inertia of stationary objects is the principle behind seismographs. A weight placed in stationary will remain in stationary unless and until a force is applied to it. The weight tries to remain stationary while the frame and drum record the relative movements. Seismometers that are highly sensitive to ground movements are used in earthquake prone areas because movements as small as 1/10,000,000 centimeters, almost small as atomic spacing have be detected at very quiet sites. Nowadays electronic modern research seismometers are used which measures the relative motion between the weight and the frame by recording the electrical voltage generated. Seismometers can record motions in all directions with simple variations in the arrangement of components [36].
Effective stress
Published in Jonathan Knappett, R. F. Craig, Craig’s Soil Mechanics, 2019
Jonathan Knappett, R. F. Craig
In the case of an earthquake, ground motion is induced as a result of powerful stress waves which are transmitted from within the Earth’s crust (i.e. far beneath the soil). As a result, liquefaction may extend to much greater depths. Combining Equations 3.12 and 3.15 ueL=icrγwz=γwGs−11+ez
Problematic soils
Published in Alan J. Lutenegger, Soils and Geotechnology in Construction, 2019
Loose, saturated, coarse-grained soils, including sands, gravels, silty sand, silty gravel, gravelly sands, and even silts, are generally considered a risk for liquefaction, given a sufficiently large enough earthquake or other dynamic loading. The key elements are that these materials exist in a loose state (low Relative Density) and that they are saturated (below the water table). Liquefaction of natural soils can be caused by strong ground motion from an earthquake, provided that the conditions are correct. In order for soils to be liquefiable in an earthquake event, several conditions are required: The soil is saturated (i.e., below the water table);The soil is predominantly coarse-grained (i.e., typically less than about 20% fines);The soil is loose (i.e., Relative Density is less than about 40%); andThe ground motion is sufficiently strong.
An Empirical Spectral Ground-Motion Model for Iran Using Truncated Iranian Strong-Motion Database Enriched by Near-Field Records
Published in Journal of Earthquake Engineering, 2023
The Iranian plateau is one of the most seismically active regions of the world. The presence of many active faults in this plateau has led to the occurrence of many earthquakes throughout its history. This region experiences many earthquakes throughout the year, so that some of them are among the most destructive earthquakes in the world. Among the important earthquakes in Iran during the last four decades, we can mention the Rudbar-Manjil (1990), Qayen (1997), Avaj (2002), Bam (2003), Firouzabad-Kojur (2004), Zarand (2005), Ahar-Varzaghan (2012), and Sarpol-e-Zahab (2017) earthquakes that resulted in loss of life, homeless people, or extensive destruction or damage to buildings (Zafarani et al. 2015). These observations show the importance of comprehensive study and investigation of earthquake characteristics in the Iranian plateau. Better understanding of ground motion characteristics and seismic hazard in the region leads to more precise earthquake-force assessment for engineering design that have a significant effect on decreasing earthquake losses and on making plans for urban development (Khodaverdian et al. 2016a, 2016b; Talebi et al. 2021; Zarrineghbal, Zafarani, and Rahimian 2021).
Seismic noise to public health signal: investigating the effects of pandemic guidance in Mexico
Published in Tapuya: Latin American Science, Technology and Society, 2022
Abril Saldaña-Tejeda, Xyoli Pérez-Campos, Elizabeth Reddy
Seismographs record ground motion. Seismologists are mainly interested in those vibrations generated by earthquakes; however, the seismic record contains vibrations from other origins, which are referred to as seismic “noise” – a term used to describe data that do not pertain to the “signals” related to ground motion that seismologists are often interested in studying. Possible sources for this “noise” include movement near instruments. This might include pedestrians, moving vehicles, or machinery in operation. To avoid collecting noise data along with the data about ground motion that they can put to use, seismologists often site instruments in places that can be somewhat isolated from human activity. However, this is not always possible. Data about the ground motion in cities (particularly in uniquely sensitive cities like Mexico City) might be unavailable to seismologists if they simply refuse to put instruments in highly populated areas. For this reason, many seismic networks include a few instruments in urban sites along with others thoroughly remote from human activity. Furthermore, The world changes around seismic stations, some once-remote instruments are now in populated places. These compromises and population changes make the seismic analysis presented here possible.
Site specific seismic hazard analysis of monumental site Dharahara, Kathmandu, Nepal
Published in Geomatics, Natural Hazards and Risk, 2022
Bikram Bhusal, Muhammad Aaqib, Satish Paudel, Hari Ram Parajuli
The study on the effect of local soil conditions to alter the induced ground motion in bedrock for Dharahara was carried out by DEEP SOIL V7 (Hashash et al. 2016). DEEP SOIL was developed at the University of Illinois and adopts Fast Fourier transform to evaluate the response of soil layers to the input ground motion. The layers and properties of soil were explicitly modelled/provided in the numerical tool with a soil model idealized as lumped MDOF system. The equations of dynamic equilibrium representing the soil model were then solved by Newmark method. The local soil condition influences the attenuation of the seismic waves and hence modifies the ground motion. The behavior of soil is non-linear and hysteretic during seismic events. The cyclic shear strain induced during seismic events increases the damping ratio (D) and reduces the shear modulus (G) as shown in Figure 5. The hysteresis stress–strain behavior with the initial shear modulus (Gmax) and secant shear modulus (G) is shown in Figure 5(a). The generalized shear modulus degradation curve and damping curve (D) are shown in Figure 5(b) and expressed in Equation (1) and (2), respectively. where WD is the area of the complete hysteresis loop and WS is the equivalent elastic stored energy.