Seismic Wave Excitation Research Articles

Impact excitation of a seismic pulse and vibrational normal modes on asteroid Bennu and associated slumping of regolith

We consider an impact on an asteroid that is energetic enough to cause resurfacing by seismic reverberation and just below the catastrophic disruption threshold, assuming that seismic waves are not rapidly attenuated. In asteroids with diameter less than 1 km we identify a regime where rare energetic impactors can excite seismic waves with frequencies near those of the asteroid’s slowest normal modes. In this regime, the distribution of seismic reverberation is not evenly distributed across the body surface. With mass-spring model elastic simulations, we model impact excitation of seismic waves with a force pulse exerted on the surface and using three different asteroid shape models. The simulations exhibit antipodal focusing and normal mode excitation. If the impulse excited vibrational energy is long lasting, vibrations are highest at impact point, its antipode and at high surface elevations such as an equatorial ridge. A near equatorial impact launches a seismic impulse on a non-spherical body that can be focused on two additional points on an the equatorial ridge. We explore simple flow models for the morphology of vibration induced surface slumping. We find that the initial seismic pulse is unlikely to cause large shape changes. Long lasting seismic reverberation on Bennu caused by a near equatorial impact could have raised the height of its equatorial ridge by a few meters and raised two peaks on it, one near impact site and the other near its antipode.

Excitation of seismic waves at the motion of fluid in the rock massive crack

The paper deals with the problem of generation of seismic radiation during the motion of a fluid in the rock massive crack. As the reason for the occurrence of seismic vibrations, a process is considered in which the interaction of a fluid and a rock causes instability of the crack walls, which leads to self-oscillations. The mathematical model describing the given process is investigated. Conclusions are made about the conditions for the occurrence of oscillations in the flow of fluid through the crack and the characteristics of the generated seismic signal.

Tutorial review of seismic surface waves’ phenomenology

In recent years, surface wave seismology has become one of the leading directions in seismological investigations of the Earth’s structure and seismic sources. Various applications cover a wide spectrum of goals, dealing with differences in sources of seismic excitation, penetration depths, frequency ranges, and interpretation techniques. Observed seismic data demonstrates the great variability of phenomenology which can produce difficulties in interpretation for beginners. This tutorial review is based on the many years’ experience of authors in processing and interpretation of seismic surface wave observations and the lectures of one of the authors (ALL) at Workshops on Seismic Wave Excitation, Propagation and Interpretation held at the Abdus Salam International Center for Theoretical Physics (Trieste, Italy) in 1990–2012. We present some typical examples of wave patterns which could be encountered in different applications and which can serve as a guide to analysis of observed seismograms.

Modeling the Excitation of Seismic Waves by the Joplin Tornado

AbstractTornadoes generate seismic signals when they contact the ground. Here we examine the signals excited by the Joplin tornado, which passed within 2 km of a station in the Earthscope Transportable Array. We model the tornado‐generated vertical seismic signal at low frequencies (0.01–0.03 Hz) and solve for the strength of the seismic source. The resulting source amplitude is largest when the tornado was reported to be strongest (EF 4–5), and the amplitude is smallest when the tornado was weak (EF 0–2). A further understanding of the relationship between source amplitude and tornado intensity could open up new ways to study tornadoes from the ground.

单层地铁车站结构地震响应分析

针对某单层地铁车站结构，建立了其三维数值计算模型，分析了其在静力、中震和大震作用下结构受力与变形，并基于现有规范对其抗震性能进行了简单评价。结果表明：1) 车站结构的柱子是其抗震的薄弱部位；2) 车站边墙与顶板和底板结合处受力较大；3) 现有的车站结构抗震性能良好，满足规范要求。论文研究成果可为类似工程的抗震设计与分析提供参考。 Three-dimensional numerical simulation calculation model was established based on a practical one-layer subway station. Structure internal forces and deformation were analyzed under static load, middle seismic and large seismic wave excitations. And also, the seismic performance of the structure was evaluated according to code. The analysis results showed that: 1) The column of the subway station is a weak part during earthquake; 2) The internal forces at the combination of side wall and bottom plate were bigger; 3) The existing subway station has good seismic performance and can satisfy the code demands. The research conclusions in the paper can provide references for seismic design and analysis of relevant projections.

Numerical Study on the Seismic Response of Structure with Consideration of the Behavior of Base Mat Uplift

The foundation might be separated from the supporting soil if the earthquake is big enough, which is known as base mat uplift. This paper proposed a simplified calculation model in which spring element is adopted to simulate the interaction between soil and structure. The load-deformation curve (F-Dcurve) of the spring element can be designated to represent the base mat uplift, in which the pressure can be applied while tensile forces are not allowed. Key factors, such as seismic wave types, seismic wave excitation directions, seismic wave amplitudes, soil shear velocities, structure stiffness, and the ratio of structure height to width (H/B), were considered in the analysis. It is shown that (1) seismic wave type has significant influence on structure response due to different frequency components it contained; (2) the vertical input of seismic wave greatly affected structure response in vertical direction, while it has little impacts in horizontal direction; (3) base mat uplift is easier to take place in soil with higher shear velocity; (4) structureH/Bvalue has complicated influence on base mat uplift. The outcome of this research is assumed to provide some references for the seismic design of the structure due to base mat uplift.

Stochastic excitation of seismic waves by a hurricane

AbstractWe investigate how a tropical cyclone (Hurricane Isaac in 2012) generated seismic ground motions using seismic and barometric data from the Earthscope network. In the frequency band 0.01–0.02 Hz, seismic and surface pressure amplitudes show a systematic decreasing trend with distance from the center of the hurricane. However, the decreasing rate is much higher for seismic waves than for pressure. We develop a stochastic theory of seismic wave excitation by surface pressure that connects these two observed data sets; surface pressure is the excitation source, and seismic data are the resulting seismic wave field. This theory contains two parameters: (i) the pressure power spectral density (Sp) and (ii) the correlation length in the pressure field (L). Using the formula, we solve for the spatial variation of correlation lengths. The solution shows that longer correlation lengths in pressure are near the hurricane center. Because seismic wave excitation is proportional to L2Sp, the excitation for seismic waves becomes effectively more localized closer to the center. Also, the scaling relation between L and Sp leads to an excitation source which is approximately proportional to the third power of surface pressure. This centralized source for seismic wave excitation explains why the decreasing rate with distance is higher for seismic data than for barometric data. However, this spatial coherence mechanism may not be the only process, as strong turbulence near the center may cause transient bursts of pressure and also induce higher temporal correlation. These alternative mechanisms need to be carefully analyzed in the future.

Comparison of seismic sources for shallow seismic: sledgehammer and pyrotechnics

AbstractThe pyrotechnic materials are one of the types of the explosives materials which produce thermal, luminous or sound effects, gas, smoke and their combination as a result of a self-sustaining chemical reaction. Therefore, pyrotechnics can be used as a seismic source that is designed to release accumulated energy in a form of seismic wave recorded by tremor sensors (geophones) after its passage through the rock mass. The aim of this paper was to determine the utility of pyrotechnics for shallow seismic engineering. The work presented comparing the conventional method of seismic wave excitation for seismic refraction method like plate and hammer and activating of firecrackers on the surface. The energy released by various sources and frequency spectra was compared for the two types of sources. The obtained results did not determine which sources gave the better results but showed very interesting aspects of using pyrotechnics in seismic measurements for example the use of pyrotechnic materials in MASW.

Heat effect in mechanical excitation of seismic waves

The authors analyze seismo-thermal effect (STE) that is the internal heating of ground under the action of external vibration and impulsive mechanical oscillation within a frequency range from units to hundred of hertz. It is found the STE has some general features such as “fatigue,” relaxation and freezing. The article reports long-term temperature monitoring under a platform of a periodically actuated vibration source. The empirical relationship for the level of STE and the depth below the vibration source platform is offered, and the interconnection of the STE level and the vibration power is shown.

20412 三次元配管の複数次モード振動を低減する高減衰合金ばねを用いた動吸振器の制振効果

The purpose of this study is to develop a three-dimensional passive dynamic damper using springs with high damping material to reduce multiple vibration modes of three-dimensional piping systems. In this paper, first, concepts for design of a three-dimensional passive dynamic damper are described. Further, multiple TMD theory is proposed as the best design method of the three-dimensional passive dynamic damper. Next, vibration tests using a dynamic damper model with high damping springs and a 3D pipe model are performed in order to investigate effects of vibration reductions of the dynamic damper model. In sine wave excitation tests, the resonance responses of 3D pipe model are reduced by using the dynamic damper model. In seismic wave excitation tests, the seismic responses in multiple modes of the 3D pipe model are reduced by the using dynamic damper model. As a result, the seismic response s of the 3D pipe model are confirmed to be greatly improved by using the dynamic damper model.

Researching of Seismic Wave Excitation Technology

Currently, the seismic wave technique increasingly used in mineral exploration, detecting buried targets etc. Conventional seismic wave excitation technique has many drawbacks. This paper summarizes the advantages and disadvantages of various seismic wave excitation technology, practical applications may need to select the appropriate source technology in order to stimulate better results.

Traveling Wave Resonance and Simplified Analysis Method for Long-Span Symmetrical Cable-Stayed Bridges under Seismic Traveling Wave Excitation

The seismic responses of a long-span cable-stayed bridge under uniform excitation and traveling wave excitation in the longitudinal direction are, respectively, computed. The numerical results show that the bridge’s peak seismic responses vary significantly as the apparent wave velocity decreases. Therefore, the traveling wave effect must be considered in the seismic design of long-span bridges. The bridge’s peak seismic responses do not vary monotonously with the apparent wave velocity due to the traveling wave resonance. A new traveling wave excitation method that can simplify the multisupport excitation process into a two-support excitation process is developed.

Rupture dynamics and ground motion from 3‐D rough‐fault simulations

AbstractWe perform three‐dimensional (3‐D) numerical calculations of dynamic rupture along non‐planar faults to study the effects of fault roughness on rupture propagation and resultant ground motion. The fault roughness model follows a self‐similar fractal distribution over length scales spanning three orders of magnitude, from ~102 to ~105 m. The fault is governed by a strongly rate‐weakening friction, and the bulk material is subject to Drucker‐Prager viscoplasticity. Fault roughness promotes the development of self‐healing rupture pulses and a heterogeneous distribution of fault slip at the free surface and at depth. The inelastic deformation, generated by the large dynamic stress near rupture fronts, occurs in a narrow volume around the fault with heterogeneous thickness correlated to local roughness slopes. Inelastic deformation near the free surface, however, is induced by the stress waves originated from dynamic rupture at depth and spreads to large distances (>10 km) away from the fault. The present simulations model seismic wave excitation up to ~10 Hz with rupture lengths of ~100 km, permitting comparisons with empirical studies of ground‐motion intensity measures of engineering interest. Characteristics of site‐averaged synthetic response spectra, including the distance and period dependence of the median values, absolute level, and intra‐event standard deviation, are comparable to appropriate empirical estimates throughout the period range 0.1–3.0 s. This class of model may provide a viable representation of the ground‐motion excitation process over a wide frequency range in a large spatial domain, with potential applications to the numerical prediction of source‐ and path‐specific effects on earthquake ground motion.

Momentum Distribution in Solar Flare Processes

We discuss the consequences of momentum conservation in processes related to solar flares and coronal mass ejections (CMEs), in particular describing the relative importance of vertical impulses that could contribute to the excitation of seismic waves (“sunquakes”). The initial impulse associated with the primary flare energy transport in the impulsive phase contains sufficient momentum, as do the impulses associated with the acceleration of the evaporation flow (the chromospheric shock) or the CME itself. We note that the deceleration of the evaporative flow, as coronal closed fields arrest it, will tend to produce an opposite impulse, reducing the energy coupling into the interior. The actual mechanism of the coupling remains unclear at present.

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

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.

Seismic response of three-dimensional rockfill dams using the Indirect Boundary Element Method

The Indirect Boundary Element Method (IBEM) is used to compute the seismic response of a three-dimensional rockfill dam model. The IBEM is based on a single layer integral representation of elastic fields in terms of the full-space Green function, or fundamental solution of the equations of dynamic elasticity, and the associated force densities along the boundaries. The method has been applied to simulate the ground motion in several configurations of surface geology. Moreover, the IBEM has been used as benchmark to test other procedures. We compute the seismic response of a three-dimensional rockfill dam model placed within a canyon that constitutes an irregularity on the surface of an elastic half-space. The rockfill is also assumed elastic with hysteretic damping to account for energy dissipation. Various types of incident waves are considered to analyze the physical characteristics of the response: symmetries, amplifications, impulse response and the like. Computations are performed in the frequency domain and lead to time response using Fourier analysis. In the present implementation a symmetrical model is used to test symmetries. The boundaries of each region are discretized into boundary elements whose size depends on the shortest wavelength, typically, six boundary segments per wavelength. Usually, the seismic response of rockfill dams is simulated using either finite elements (FEM) or finite differences (FDM). In most applications, commercial tools that combine features of these methods are used to assess the seismic response of the system for a given motion at the base of model. However, in order to consider realistic excitation of seismic waves with different incidence angles and azimuth we explore the IBEM.

Local seismologic observations of karst processes

The paper addresses the methodic questions of arrangement and implementation of local temporal seismologic observations targeting research on karst. We describe an approach for the quantitative assessment of the feasibility for recording the seismic effect of dynamic phenomena accompanying the karst processes. The approach copes with the specific features of excitation, propagation, and recording of seismic waves for a given karsting massif. The adequacy of this approach is supported by the results of experiments on the imitation of collapses in the test object, namely in the Kungur ice cave (Perm region). We describe the experience in application of approaches developed in “big” seismology in the choice of the optimal configuration of the local seismic group (taking into account the properties of stationary microseismic noises) and methods for data processing (identification of the nature of signals) as applied to the conditions of the study of karst processes. Based on the observations performed in Kungur, Perm region, the efficiency of the use of the local seismic group for discriminating signals of an exogenous and endogenous nature is demonstrated.

Vertical seismic profiling on the sea shelf

Results of a numerical experiment on vertical seismic profiling of the sea bottom on the shelf are presented. The results are obtained by analyzing the acoustic fields in the shelf area with the use of both hydroacoustic and seismic bottom sources of radiation. The influence of both transmission depth and source type on the efficiency of seismic wave excitation in the bottom is investigated. The formation of the vertical wave hodographs and its dependence on the acoustic parameters and structure of the bottom in the oceanic shelf region is analyzed. A high sensitivity of the vertical wave hodographs to variations in the parameters of the bottom medium is revealed. For the layered bottom model, the possibility of estimating the positions of layer boundaries in depth and the velocities of waves within the layers is demonstrated.

1968年十勝沖地震(<I>M</I>=7.9)と1994年三陸はるか沖地震(<I>M</I>=7.6)の震度から推定される短周期地震波発生域

The Tokachi-oki earthquake (M=7.9) of May 16, 1968 and the Sanriku-Haruka-oki earthquake (M=7.6) of December 28, 1994 have a partially common source area and the 1968 event consists of two asperities, southern one of which took a role of asperity once again for the 1994 event. Short-period seismic wave radiation zones (SPRZs) have been evaluated for both the events from the inversion analysis of seismic intensity data. We also identified their energy centroids of all the SPRZs. It was concluded that the every centroid of SPRZ was located at the edge of corresponding asperities of the 1968 and the 1994 earthquakes in the forward direction of fault rupture. One SPRZ was located near the terminal slip points in the southern asperity for the 1968 event and was active recurrently for the 1994 event as well as asperity. We calculated magnitude m for both the SPRZs for the 1968 and the 1994 event. m from the southern SPRZ of the 1968 event was larger than that from the SPRZ of the 1994 event. This suggested that the short-period seismic wave excitation from the asperity of the multiple-segment rupture event is larger than that from the same asperity for the single-segment rupture event occurring from the same segment.

Minimal cut-based recursive decomposition algorithm for seismic reliability evaluation of lifeline networks

In this paper, a new probabilistic analytical approach, the minimal cut-based recursive decomposition algorithm (MCRDA), is presented to evaluate the seismic reliability of large-scale lifeline systems. Based on the minimal cut searching algorithm, the approach calculates the disjoint minimal cuts one by one using the basic procedure of the recursive decomposition method. At the same time, the process obtains the disjoint minimal paths of the system. In order to improve the computation efficiency, probabilistic inequality is used to calculate a solution that satisfies the prescribed error bound. A series of case studies show that MCRDA converges rapidly when the edges of the systems have low reliabilities. Therefore, the approach can be used to evaluate large-scale lifeline systems subjected to strong seismic wave excitation.