Total Seismic Energy Research Articles

Coseismic Deformation of the Earth’s Surface in the Area of the Catastrophic 2008 Wenchuan Earthquake According to GPS Measurements

The occurrence time prediction of the strongest earthquakes is one of most topical tasks of seismology. Appearing in the recent years, new observation methods for precursors of different nature can open avenues to achieve success in the field of medium-term seismic forecast. One such method is to observe the Earth’s surface deformation using the Global Positioning System (GPS). Such a region is the territory of South-Western China, where in 2008 occurred the catastrophic Wenchuan earthquake, which caused very large destruction of infrastructure and huge human losses. This GPS system has been in operation since 1991 in the eastern part of the Qinghai–Tibet Plateau, the Sichuan Basin, and the Yunnan–Guizhou Plateau. The results of these observations have already been published and can be applied to study of the activity and segmentation of faults. Until 2004, the measurement network covering the Longmen Shan fault zone and the adjacent territory consisted of ten major points and some additional ones. The 1991–2001 data of GPS observations show that in the Longmen Shan fault zone was recorded offset to the northeast with a relatively low rate of 2.3 mm/year. As a result of studying the surface horizontal deformation using GPS observations, it was established that the focus area in 1999–2007 (prior to the strongest earthquake of 2008) was characterized by anomalously low rates of horizontal movements. This was probably related to the accumulation of stresses in the crust. It can be concluded retrospectively that the results of GPS observations could be considered as a medium-term precursor of the 2008 Wenchuan earthquake, which showed the location of the future seismic source position. The length of the zone of relatively weak horizontal displacements exceeded 250 km, which statistically correspond to a magnitude about 8 earthquake. The seismic rupture system (with a total length of ~240 km, originating during the 2008 Wenchuan earthquake) was confined to the NE-trending Longmen Shan fault zone, which occurs between the eastern margin of the Qinghai–Tibet Plateau and the northwestern part of the Sichuan Basin. Immediately after the Wenchuan event, the pattern of distribution of rates of horizontal movements has greatly changed. The horizontal deformations spanned most of the territory adjacent to the seismic fault zone, and the Longmen Shan Fault Zone exhibited the tectonic reduction of the surface at the expense of reversed movements of fault wings toward each other. The amplitudes of horizontal movements at equal distance on both sides of the branch of the Yingxiu–Beichuan main seismic rupture to the west are reduced slowly, and to the east – quickly. The vertical coseismic surface deformation, registered using satellite geodesy in the epicentral area of the seismic event, were mainly expressed in the submergence of the surface by different amounts in the southeastern wing of the Longmen Shan fault zone in the Sichuan Basin. It can be concluded on the basis of an analysis of the total seismic energy release during the earthquake that the period of 1991–2007 was an evident stage of seismic calm period prior to the strongest earthquake, whereas a period of seismic activity has been registered since 2008 (at the moment of the major shake) up to the present and may last several more years. The extremely low rate of horizontal displacements in the epicentral area of the preparing strongest earthquake can be considered as a middle-term precursor of its occurrence place.

Long-Period, Long-Duration Seismic Events and Their Probable Role in Reservoir Stimulation and Stage Productivity

SummaryHydraulic fracturing is a well-established technique to extract gas or liquid hydrocarbons from low-permeability formations such as shale and tight gas reservoirs. Diffusion of hydrofracturing fluid outward from the stimulated fractures into the target formation produces slip across pre-existing fractures and other discontinuities in the rock. Microseismic events recorded by downhole seismic-monitoring arrays are a manifestation of associated deformation. Recent investigations suggest that the total cumulative seismic moment of microearthquakes during hydraulic fracturing is only a small portion of the total seismic-energy release expected for the fluid volume injected into the formation. These observations suggest that other sources of energy release (such as inelastic deformation), contemporaneous with microseismicity, should be considered relevant to the hydraulic-fracturing process. Recent observations on long-period, long-duration (LPLD) seismic events suggest that slow slip emission along weaknesses that are misaligned with respect to the present-day stress field is likely an important mechanism of deformation and should be better understood and quantified in reservoir stimulations. In Morgantown, West Virginia, we conducted seismic monitoring of hydraulic-fracturing activity using an array of five broadband, three-component (3C) surface seismometers. Using this network, we identified 89 high-amplitude, impulsive events and 436 LPLD events, with highly emergent waveform characteristics. In these interpreted LPLD events, we observed a significant concentration of energy in the 0.8- to 3-Hz frequency range. During hydraulic fracturing, LPLD events were found to occur most frequently when the pumping pressure and rate were at or near maximum values. Because the main purpose of hydraulic fracturing is to stimulate oil and gas production from the less-permeable reservoir, we compared the relative production contributions/stage to the frequency of the occurrence of suspected LPLD events. We found a positive correlation between the frequency of LPLD events and stage-by-stage gas production, highlighting the potential contribution of slow deformation processes and its effectiveness in the reservoir stimulation.

Earthquake Lights: Mechanism of Electrical Coupling of Earth's Crust to the Lower Atmosphere

AbstractEarthquake lights are an atmospheric luminous phenomenon occurring before, during, and occasionally after earthquakes. In the present work we assume that strong electric currents are produced inside the Earth during earthquakes and model the current and field distribution inside and above the Earth to find the conditions where electrical discharges can appear. The simulation results quantify the effects of various configurations of current dipoles inside the Earth. The results are supported by approximate formulations allowing effective solution of the same problems using an analytical theory. It is shown that a large‐scale dipole with poles located in Earth's crust at 5 and 15 km beneath the Earth's surface requires energy significantly higher than the total seismic wave energy in major earthquakes. The more likely setup to produce earthquake lights is found to be when the upper pole of the source current dipole is shifted close to the Earth's surface, in particular, when locations of current dipoles are tens of meters beneath Earth's surface.

Comparison of seismic effects during deep tunnel excavation with different methods

The rapid release of strain energy is an important phenomenon leading to seismic events or rock failures during the excavation of deep rock. Through theoretical analysis of strain energy adjustment during blasting and mechanical excavation, and the interpretation of measured seismicity in the Jin-Ping II Hydropower Station in China, this paper describes the characteristics of energy partition and induced seismicity corresponding to different energy release rates. The theoretical analysis indicates that part of the strain energy will be drastically released accompanied by violent crushing and fragmentation of rock under blast load, and this process will result in seismic events in addition to blasting vibration. The intensity of the seismicity induced by transient strain energy release highly depends on the unloading rate of in-situ stress. For mechanical excavation, the strain energy, which is mainly dissipated in the deformation of surrounding rock, releases smoothly, and almost no seismic events are produced in this gradual process. Field test reveals that the seismic energy transformed from the rock strain energy under high stress condition is roughly equal to that coming from explosive energy, and the two kinds of vibrations superimpose together to form the total blasting excavation-induced seismicity. In addition, the most intense seismicity is induced by the cut blasting delay; this delay contributes 50% of the total seismic energy released in a blast event. For mechanical excavation, the seismic energy of induced vibration (mainly the low intensity acoustic emission events or mechanical loading impacts), which accounts only for 1.5‰ of that caused by in-situ stress transient releasing, can be ignored in assessing the dynamic response of surrounding rock.

Modeling injection-induced seismicity through calculation of radiated seismic energy

Seismicity induced by the injection of fluid into the fractured ground is one of the most challenging issues facing geothermal and deep wastewater disposal industries. This paper introduces an energy-based numerical methodology to study roles of fluid injection in triggering rupture (seismic slip) along preexisting faults. The methodology is developed in the Universal Distinct Element Code (UDEC) using its quasi-static and dynamic schemes and calculates the total seismic energy radiated by a rupture when more energy is made available in the system than can be stored or consumed. As an example of the application of the developed methodology, we study effects of fluid injection on rupture dynamics by pressurizing a single fault surrounded by impermeable rock, representing a simplified analogy for the injection process in deep wastewater disposal and geothermal activities. We discuss effects of raising the fluid pressure on initiating rupture over well-oriented (or critically loaded) and misoriented faults. Results show that fluid injection can trigger a rupture along both well-oriented and misoriented faults although the notion of seismicity may be observed along the well-oriented fault as early as the beginning of the injection process. The well-oriented fault generates higher seismic energy magnitude as more energy is available for rupture due to the higher peak shear stress and stress drop on the fault. Making simplifying assumptions, this study also found that fluid can be injected under a high-pressure increment before and after the fault initial activation while the radiated seismic energy remains relatively insignificant. However, gradually increasing the fluid pressure at the onset of rupture reduces the radiated seismic energy by 30%. Comparing the seismic moment and radiated seismic energy for each event reveals that while radiated seismic energy varies between different values of pressure increment, the calculated seismic moment stays constant, showing the possible ineffectiveness of the seismic moment in representing the intensity of injection-induced ruptures.

Forecasting of future earthquakes in the northeast region of India considering energy released concept

This study presents the forecasting of time and magnitude size of the next earthquake in the northeast India, using four probability distribution models (Gamma, Lognormal, Weibull and Log-logistic) considering updated earthquake catalog of magnitude Mw ≥ 6.0 that occurred from year 1737–2015 in the study area. On the basis of past seismicity of the region, two types of conditional probabilities have been estimated using their best fit model and respective model parameters. The first conditional probability is the probability of seismic energy (e × 1020 ergs), which is expected to release in the future earthquake, exceeding a certain level of seismic energy (E × 1020 ergs). And the second conditional probability is the probability of seismic energy (a × 1020 ergs/year), which is expected to release per year, exceeding a certain level of seismic energy per year (A × 1020 ergs/year). The logarithm likelihood functions (ln L) were also estimated for all four probability distribution models. A higher value of ln L suggests a better model and a lower value shows a worse model. The time of the future earthquake is forecasted by dividing the total seismic energy expected to release in the future earthquake with the total seismic energy expected to release per year. The epicentre of recently occurred 4 January 2016 Manipur earthquake (M 6.7), 13 April 2016 Myanmar earthquake (M 6.9) and the 24 August 2016 Myanmar earthquake (M 6.8) are located in zone Z.12, zone Z.16 and zone Z.15, respectively and that are the identified seismic source zones in the study area which show that the proposed techniques and models yield good forecasting accuracy.

Modified pseudo-dynamic bearing capacity analysis of shallow strip footing considering total seismic wave

The seismic bearing capacity analysis is a very important study for the safe design of underground structures in earthquake-prone areas. The earlier pseudo-dynamic methods provide the methodology of seismic analyses without considering the effects of Rayleigh waves though it contributes about 67% of the total seismic energy. So, in this paper, an attempt has been made to evaluate the seismic bearing capacity of shallow strip footing using modified pseudo-dynamic approach. This approach simultaneously considers the effect of Rayleigh wave along with primary wave and shear wave velocity. Limit equilibrium method is used to solve this problem of seismic bearing capacity of shallow strip footing resting on c–Φ soil. Along with that single seismic bearing capacity, coefficients are presented under simultaneous resistance of unit weight, overburden and cohesion and detailed analyse w.r.t different parameters. Also, results are thoroughly compared with the existing values in the literature and the significance of the present methodology for designing the shallow strip footing is discussed.

Active vibration control of seismic excitation

Seismic wave control is very important both in civil and mechanical engineering. Common passive methods for isolating a building or a device include base isolators and tuned mass dampers. In the present paper, a time-varying controllable spring is considered as a vibration isolator for a linear mechanical system. The controller works as follows: When the seismic movement is active, the velocity of the moving mass is monitored as the reference velocity. When such reference velocity is positive, the stiffness is reduced; when it is negative, the stiffness is increased. Numerical investigations show that the controller is capable of filtering seismic excitation close to the natural frequency of the controlled system and reducing the total seismic energy transfer up to 5 times. The role played by the gravity in the active vibration filtering is pointed out by showing that no filtering action can be observed in gravity-free simulations. Moreover, control effectiveness has been proven for a measured seismic signal, showing its robustness in presence of noise.

Differences of precursory seismic energy release for the 2007 effusive dome-forming and 2014 Plinian eruptions at Kelud volcano, Indonesia

Early warnings of the timing, style, and size of volcanic eruptions, made on the basis of seismic monitoring, are important for mitigation of the hazards associated with volcanic eruptions. We calculated the rates of seismic energy release at Kelud volcano, Indonesia, preceding both the 2007 effusive lava-dome eruption and the 2014 Plinian eruption. For the 2007 eruption, there was first a step-wise increase in the rate of release of seismic energy, followed by a gradual decrease until the eruption. For the 2014 eruption, the rate of energy release was almost constant until 10days before the eruption, then gradually increased until there was a dramatic acceleration during the last day before the eruption. The total seismic energy released by the 2007 and 2014 eruptions were 3×108J and 2.2×109J, respectively. The relative difference between the ejected volumes of the 2007 and 2014 eruptions is roughly equivalent to that of the total seismic energy released preceding the eruptions. We conducted several trials of the material failure forecast method (FFM), applying it to the square root of the rate of seismic energy released, to assess its usefulness for predicting the timing of eruptions. The predicted onset of the 2007 eruption was one day earlier than the actual eruption and the seismic energy release preceding the actual eruption did not increase dramatically as suggested by the FFM model. Several trials of FFM for the 2014 eruption predicted the onset of the eruption to be three days to two weeks later than the actual eruption. Even as the end time of the FFM time window approaches several hours to 10min before the actual eruption onset, the predicted eruption onset is still 3h later than the actual onset. Thus, the results of our FFM modeling did not show the method to be useful for predicting eruption times for Kelud volcano. The differences of the FFM modeling results for the 2007 and 2014 eruptions likely reflect the differences in the rate of energy release immediately before the two eruptions: a deceleration before the 2007 eruption and an acceleration before the 2014 eruption. These differences may reflect differences in precursory processes for effusive lava-dome and Plinian eruptions.

Time lag between deformation and seismicity along monogenetic volcanic unrest periods: The case of El Hierro Island (Canary Islands)

AbstractBetween 2011 and 2014 there were at least seven episodes of magmatic intrusion in El Hierro Island, but only the first one led to a submarine eruption in 2011–2012. In order to study the relationship between GPS deformation and seismicity during these episodes, we compare the temporal evolution of the deformation with the cumulative seismic energy released. In some of the episodes both deformation and seismicity evolve in a very similar way, but in others a time lag appears between them, in which the deformation precedes the seismicity. Furthermore, a linear correlation between decimal logarithm of intruded magma volume and decimal logarithm of total seismic energy released along the different episodes has been observed. Therefore, if a future magmatic intrusion in El Hierro Island follows this behavior with a proper time lag, we could have an a priori estimate on the order of magnitude the seismic energy released would reach.

Causal mechanisms of seismo-EM phenomena during the 1965\u20131967 Matsushiro earthquake swarm

The 1965–1967 Matsushiro earthquake swarm in central Japan exhibited two unique characteristics. The first was a hydro-mechanical crust rupture resulting from degassing, volume expansion of CO2/water, and a crack opening within the critically stressed crust under a strike-slip stress. The other was, despite the lower total seismic energy, the occurrence of complexed seismo-electromagnetic (seismo-EM) phenomena of the geomagnetic intensity increase, unusual earthquake lights (EQLs) and atmospheric electric field (AEF) variations. Although the basic rupture process of this swarm of earthquakes is reasonably understood in terms of hydro-mechanical crust rupture, the associated seismo-EM processes remain largely unexplained. Here, we describe a series of seismo-EM mechanisms involved in the hydro-mechanical rupture process, as observed by coupling the electric interaction of rock rupture with CO2 gas and the dielectric-barrier discharge of the modelled fields in laboratory experiments. We found that CO2 gases passing through the newly created fracture surface of the rock were electrified to generate pressure-impressed current/electric dipoles, which could induce a magnetic field following Biot-Savart’s law, decrease the atmospheric electric field and generate dielectric-barrier discharge lightning affected by the coupling effect between the seismic and meteorological activities.

Total energy of deep low‐frequency tremor in the Nankai subduction zone, southwest Japan

AbstractWe estimated the total seismic energy of deep low‐frequency tremor in the Nankai subduction zone, southwest Japan, over an 11 year period. For precise estimation, the continuous time sequence of tremor activity was carefully detected using a procedure designed to minimize false‐negative detections. The estimated spatial distribution of accumulated total energy of tremor indicates high‐energy area in the western Shikoku region. Tremor activity rate, defined as the yearly average of total tremor energy per unit area, was investigated in each area throughout the Nankai subduction zone. The tremor activity rate was spatially variable, being high in areas west of the Kii Channel (the channel is marked by a complex plate geometry) and low in areas east of the channel. The plate convergence rate shows the same spatial pattern as that for tremor activity. We infer that tremor activity is influenced by accumulated strain due to plate convergence.

Four Years of Daily Photon Emissions That Have Predicted Major Earthquakes: Raw Data, Spectral Power Density Analyses and Implications for the Geosciences

The daily median ground surface flux densities per day from a continuously operating photomultiplier tube unit for four years in Sudbury, Ontario are presented for December 2010 to December 2014. Increases of about 2 to 4 PMT units (1 unit = 5 × 10-11 W·m-2) for median daily measures reliably occurred about two weeks before M ≥ 7.7 earthquakes anywhere on the planet. The PMT units, until June 2014, usually returned to baseline within a few days after the events. There has been a slow positive drift in flux power density since about 2012 and a conspicuous maintained increase after May, 2014. The equivalent energy per day if it were represented isotropically within the volume occupied by the earth is the same order of magnitude as the average daily global total seismic energy release. Spectral power densities revealed enhanced peaks (periodicities) between 100 to 150 days, 60 days, 30 days, and 25 days. Discriminable peaks in power were noted around 18 days, 14 days, and 4 to 6 days. These results suggest that continuous measurement of photonemissions within hyper-dark conditions may reveal geophysical processes that precede larger seismic events and could reflect the movement of the earth-solar system around the galactic center.

Variable Star Symbols for Seismicity Plots

Online Material: Maps of seismicity and cities; test sheet; list of earthquakes; Fortran 77 code. At least since Mallet (1858) seismicity maps have been a way of showing earthquake activity, but, because earthquake size varies greatly, it is difficult to provide an accurate representation of the spatial variation of total seismic energy or moment release. The most common approach, using for each earthquake a single geometric figure of varying size, creates substantial overlap between large symbols. To reduce overlap and provide a more distinctive gradation, I propose a family of symbols in which size and shape vary together, from polygonal to star shaped as their size increases. Two functions determine how symbol size and shape vary with value, and even a simple parametrization gives considerable flexibility in symbol design. Tests show that, given an appropriate key, the symbol value can be estimated to within better than 5% of the range covered. Symbolization in seismicity maps is challenging. Using identical symbols plotted at the epicenters (or, in a cross section, the hypocenters) shows where there are more or fewer earthquakes but not how (say) moment release is distributed. This can be done by spatially smoothing the amount of energy or moment release and contouring the result (e.g., Allen et al. , 1965), but this in turn removes fine details. Most seismicity maps use a simple geometrical figure, usually a circle or square, to symbolize for each earthquake and vary its size with the earthquake magnitude. The interior of each symbol can be filled with a color to denote depth (or, in Web displays, recency of occurrence). One problem with this approach is that one large symbol can easily cover many small ones. Some seismicity maps use two geometrical figures, one (often a scaled circle) for events less than some magnitude and another …

Active seismic sources as a proxy for seismic surface processes: An example from the 2012 Tongariro volcanic eruptions, New Zealand

The 6 August 2012 eruption from Tongariro volcano's Te Maari vent comprised a complex sequence of events including at least 4 eruption pulses, a large chasm collapse, and a debris avalanche (volume of ~7×105m3) that propagated ~2km beyond the eruptive vent. The eruption was poorly observed, being obscured by night time darkness, and the eruption timing must be unravelled instead from a complex seismic record that includes discrete volcanic earthquakes, a sequence of low to moderate level spasmodic tremor and an intense burst of seismic and infrasound activity that marked the eruption onset. We have discriminated the evolution of the complex surface activity by comparing active seismic source data to the seismic sequence in a new cross correlation source location approach. We dropped 11 high impact masses from helicopter to generate a range of active seismic sources in the vicinity of the eruption vent, chasm, and debris avalanche areas. We obtained 8 successful drops having an impact energy ranging from 3 to 9×106Nm producing observable seismic signals to a distance of 5 to 10km and having good signal to noise characteristics in the 3–12Hz range. For the 8 drops, we picked first-P arrival times and calculated amplitude spectra for a uniform set of four stations. We then compared these proxy source excitations to the natural eruption and pre-eruption data using a moving window cross correlation approach. From the correlation processing, we obtain a best matched source position in the near vent region for the eruption period and significant down channel excitations during both the pre and post eruption periods. The total seismic energy release calculated from the new method is ~8×1011Nm, similar to an independently estimated calculation based on the radiated seismic energy. The new energy estimate may be more robust than those calculated from standard seismic radiation equations, which may include uncertainties about the path and site effects. The active source data carry this information directly in the waveforms, yielding a simple conversion between seismic amplitude and energy.

Active Earth Pressure on Retaining Wall Supporting c-Φ Backfill Considering Rayleigh Wave

Study of seismic active earth pressure is very much important for the safe design of retaining walls in the earthquake prone area. The earlier analytical methods provides the methodology of computation of seismic active earth pressure without considering the effects of Rayleigh waves though it constitutes about 67 % of the total seismic energy. In this present analysis a new methodology is proposed by considering the Rayleigh wave along with the shear wave velocity (V s ) and primary wave velocity (V p ). Using the limit equilibrium principle, a methodology is developed to calculate the pseudo-dynamic active earth pressure on the back of battered-faced retaining walls supporting cohesive-frictional backfill. Results are presented in both tabular and graphical non-dimensional form. Effects of a wide range of variation of parameters like wall inclination angle (α), wall friction angle (δ), soil friction angle (Φ), horizontal and vertical seismic accelerations (k h , k v ) have been studied on the seismic active earth pressure coefficients.

Source parameters and scaling relations for small earthquakes in the Kachchh region of Gujarat, India

The scaling relationships for stress drop and corner frequency with respect to magnitude have been worked out using 159 accelerograms from 34 small earthquakes (M w 3.3–4.9) in the Kachchh region of Gujarat. The 318 spectra of P and S waves have been analyzed for this purpose. The average ratio of P- to S-wave corner frequency is found to be 1.19 suggestive of higher corner frequency for P wave as compared to that for S wave. The seismic moments estimated from P waves, M 0(P), range from 1.98 × 1014 N m to 1.60 × 1016 N m and those from S waves, M 0(S), range from 1.02 × 1014 N m to 3.4 × 1016 N m with an average ratio, M 0(P)/M 0(S), of 1.11. The total seismic energy varies from 1.83 × 1010 J to 2.84 × 1013 J. The estimated stress drop values do not depend on earthquake size significantly and lie in the range 30–120 bars for most of the events. A linear regression analysis between the estimated seismic moment (M 0) and corner frequency (f c) gives the scaling relation M 0 f c 3 = 7.6 × 1016 N m/s3. The proposed scaling laws are found to be consistent with similar scaling relations obtained in other seismically active regions of the world. Such an investigation should prove useful in seismic hazard and risk-related studies of the region. The relations developed in this study may be useful for the seismic hazard studies in the region.

New Method to Compute Seismic Active Earth Pressure on Retaining Wall Considering Seismic Waves

In earthquake prone areas, calculation of seismic active earth pressure on retaining wall is very important. Analytical methods till date for computation of seismic active earth pressure do not consider the effect of Rayleigh wave though it constitutes about 67 % of the total seismic energy. In this paper a new dynamic approach is proposed by considering all possible seismic waves viz. primary, shear and Rayleigh waves for estimation of seismic active earth pressure on rigid retaining wall by satisfying all the boundary conditions. Limit equilibrium method is used for estimation of optimised seismic active earth pressure for a rigid retaining wall supporting cohesionless backfill with critical combinations of seismic accelerations. The seismic influence zone obtained in this study is about 22 and 17 % larger when compared with available pseudo-static and pseudo-dynamic methods respectively, which indicates the significant effect of Rayleigh wave. Also, there is an increase of about 14 and 6 % in seismic active earth pressure coefficient when the present results are typically compared with pseudo-static and pseudo-dynamic methods respectively. Moreover present results compare well with the available experimental results. Present results are more critical for the design estimation of seismic active earth pressure by considering all major seismic waves as proposed in the new dynamic approach.

Pseudo-dynamic passive resistance of battered-faced retaining wall supporting c-Φ backfill considering Rayleigh wave

The concept of seismic passive resistance is very much essential for the design of retaining walls under seismic loading conditions, as the damage of such earth structures may lead to catastrophic failure. The earlier analytical methods provide the methodology of computation of seismic passive resistance without considering the effects of Rayleigh waves though it considers about 67% of the total seismic energy. In this present analysis, a new methodology is proposed by considering the Rayleigh wave along with the shear wave velocity (Vs) and primary wave velocity (Vp). Using the limit equilibrium principle, a methodology is developed to calculate the pseudo-dynamic passive resistance on the back of battered-faced retaining walls supporting cohesive-frictional backfill. Results are presented in both tabular and graphical non-dimensional forms. Effects of a wide range of variation of parameters such as wall inclination angle (α), wall friction angle (δ), soil friction angle (Φ), and horizontal and vertical seismic accelerations (kh, kv) have been studied on the seismic passive resistance coefficients.

New Approach to Determine Seismic Passive Resistance on Retaining Walls Considering Seismic Waves

AbstractCalculation of seismic earth pressure is important for design of retaining walls in earthquake-prone areas. Existing analytical methods for computation of seismic passive earth pressure do not consider the effect of Rayleigh waves, although they constitute about 67% of the total seismic energy. In this paper, a new dynamic approach is proposed by considering primary, shear, and Rayleigh waves for estimation of seismic passive earth pressure by satisfying all the boundary conditions including a zero-stress condition at the ground surface. The limit equilibrium method is used to calculate seismic passive earth pressure for a rigid retaining wall supporting cohesionless backfill with critical combinations of seismic accelerations. The seismic influence zone obtained in this study is about 23 and 14% larger compared with available pseudostatic and pseudodynamic methods, respectively, which indicates the effect of Rayleigh waves. Also, there is a decrease of 22 and 3% in seismic passive earth pressure ...