Dynamic response of Zelazny Most tailings dam to mining induced extreme seismic event occurred in 2016

The paper deals with the stability analysis of tailings dam subjected to dynamic loading induced by mining shocks which occurred in neighbouring copper mine. The main goal of the paper was to model the dynamic response of the dam during two extreme paraseismic events which occurred in 2016 based on accelerograms recorded at the dam toe. Dynamic response of the tailings dam was calculated using finite element method and the implicit time-integration method implemented in commercial codes. The boundary condition corresponding to dynamic loading was determined by deconvolution procedure. The error analysis showed that most precise signal reproduction is achieved while using target signal with peak value reduced by 40% as a test signal. Both acceleration and displacement time-series were successfully reproduced. Moreover, the stability analysis was conducted for five independent signals with design peak horizontal acceleration and showed that no permanent displacements should occur. The temporary horizontal displacement of the dam crest should not exceed 13 mm, assuming equivalent linear material model.

PROPERTIES OF THE GROUND MOTIONS PARAMETERS NEAR THE EARTHQUAKE FOCUS

Представлены дополнения в базу данных сильных движений: введены записи за 2015 г. с интенсивностью от 5 баллов, а также записи с эпицентральным расстоянием не больше 7 км с любой интенсивностью. Проведено исследование зависимости средних значений параметров грунтовых движений от гипоцентрального расстояния в ближней зоне землетрясения в интервалах: 0–5, 5–10, 10–15, 15–20, 20–25, 25–30, 30–40, 40–50, 0–50, 50–2000, 0–2000 км. Проведена оценка статистической значимости зависимостей. Показано, что параметры грунтовых движений имеют экстремальную точку при гипоцентральных расстояниях около 20 км, которую можно считать границей между ближней и дальней зоной землетрясения. Показано, что отношение пикового вертикального ускорения к пиковому горизонтальному ускорению (PVA/PHA) коррелирует с магнитудой события – чем выше магнитуда, тем больше значение PVA/PHA при равных прочих условиях Additions into the Strong Motions Data Base are represented: records 2015 year with the intensity from 5, and also the records with epicentral distance not greater than 7 km with any intensity. A study of the ground motions parameters average values dependence on the hypocentral distance in the neighbor zone of earthquake in the intervals: 0–5, 5–10, 10–15, 15–20, 25–30, 30–40, 40–50, 0–50, 50–2000, 0–2000 km is carried out. The estimation of the statistical significance of dependences is carried out. It is shown that the parameters of ground motions have the extreme point with the hypocentral distances about 20 km, which can be considered as the boundary between the near and far zone of earthquake. It is shown that the ratio of peak vertical acceleration to the peak horizontal acceleration (PVA/PHA) correlates with the magnitude of event – the higher the magnitude, the greater the value PVA/PHA under otherwise equal conditions.

INFLUENCE OF THE SOILS TYPES ON THE STRONG GROUND MOTIONS INTENSITY

Проведено исследование влияния различных видов грунтов на интенсивность проявления сильных грунтовых движений на примере записей базы данных, созданной авторами. Для различных типов грунта (скала, песок, гравий, ил, глина) получены корреляционные зависимости интенсивности от логарифма пикового горизонтального ускорения и от гипоцентрального расстояния по отдельности. Показано, что при высоких магнитудах интенсивность проявляется на различных грунтах в порядке убывания следую- щим образом: глина, песок, ил, гравий, скала. Проведенное исследование показало слабую зависимость интенсивности от скорости поперечной волны. Проведеное сравнение корреляционных зависимостей интенсивности от магнитуды и от гипоцентрального расстояния для записей базы данных SMDBCGI с уравнением Шебалина, показало что точность формулы авторов для всех типов грунтов и формулы Шебалина одинакова в пределах ошибки. Показано, что для станций системы KNET лучше использовать формулу корреляционной зависимости интенсивности от магнитуды и от логарифма пикового горизонтального ускорения, чем от магнитуды и от логарифма гипоцентрального расстояния Study of the different soils forms influence on the intensity of the strong ground motions manifestation based on the records data base, created by the authors is carried out. The correlation dependences of intensity on the logarithm of peak horizontal accelerationandon the hypocentral distance separately are obtained for different types of soil (rock, sand, gravel, silt, clay). For the different groundswith the high magnitudes the intensity valueis in follows descending order: clay, sand, silt, gravel, rock. The conducted investigation showed the weak dependence of intensity on the transverse wave speed. The comparison of the correlation dependences of intensity on the magnitude and on the hypocentral distance for records of database SMDB CGI with Shebalin formula showed thatthe accuracy of the authors formula for all types of grounds and Shebalin formula is identical in the ranges of error. For the system KNET stations it is better to use the formula of correlation dependence of intensity on the magnitude and on the logarithm of peak horizontal acceleration, than the correlation dependence on the magnitude and on the hypocentral distance logarithm

PROBABILISTIC SEISMIC HAZARD MAPS OF THAILAND

In this study, the probabilistic seismic hazard map of Thailand and neighboring areas is developed. Thailand is located close to the Andaman thrust in the west and the Sunda arc in the south which are the boundaries between the Eurasian plate and Indo-Australian plate. Several active faults in this region have caused earthquakes which affects Thailand. Earthquakes recorded from 1912 to 2006 by the Thai Meteorological Department and the US Geological Survey are used in the analysis. Two attenuation models for active tectonic regions which give good correlations with actual measured accelerations are used in predicting peak horizontal accelerations in Thailand. Maps of peak horizontal accelerations at rock sites with 2% and 10% probabilities of exceedance in 50 years are developed. For the peak horizontal acceleration with 10% probability of exceedance in 50 years, the maximum accelerations are about 0.25 g in the northern part of Thailand and 0.02 g in Bangkok. For the peak horizontal acceleration with 2% probability of exceedance in 50 years, the maximum accelerations are about 0.4 g in the northern part of Thailand and 0.04 g in Bangkok.

Ground Motion Attenuation Model for Peak Horizontal Acceleration from Shallow Crustal Earthquakes

Spatial distribution of ground motion data of recent earthquakes unveiled some features of peak ground acceleration (PGA) attenuation with respect to closest distance to the fault ( R) that current predictive models may not effectively capture. As such, PGA: (1) remains constant in the near-fault area, (2) may show an increase in amplitudes at a certain distance of about 3–10 km from the fault rupture, (3) attenuates with slope of R−1 and faster at farther distances, and (4) intensifies at certain distances due to basin effect (if basin is present). A new ground motion attenuation model is developed using a comprehensive set of ground motion data compiled from shallow crustal earthquakes. A novel feature of the predictive model is its new functional form structured on the transfer function of a single-degree-of-freedom oscillator whereby frequency square term is replaced with closest distance to the fault. We are proposing to fit ground motion amplitudes to a shape of a response function of a series (cascade) of filters, stacked separately one after another, instead of fitting an attenuation curve to a prescribed empirical expression. In this mathematical model each filter represents a separate physical effect.

The great Mexican earthquake of 19 June 1858: Expected ground motions and damage in Mexico City from a similar future event

The description of the great earthquake of 19 June 1858 is unusual: damage and high intensities were reported both in the state of Michoacan and in Mexico City. Although a coastal epicenter for this earthquake cannot be ruled out, the reports agree better with an intermediate-depth (about 50 km), normal-faulting event in the subducted Cocos plate. A careful examination of the reports of this event and other normal-faulting events below the Mexican altiplano suggests that a likely location is 18.0 °N, 100.8 °W, near the epicenter of the 6 June 1964 (M7.3, H = 55 km) event. This location is 220 km SW of the city. The magnitude of the earthquake is estimated to be about 7.7. We synthesize expected ground motions in CU, a hill-zone site in the city, from an event similar to that of 1858, using records from the 23 May 1994 earthquake (18.0 °N, 100.6 °W, H = 50 km, M5.7) as an empirical Green's function and stress parameter, Δσ, of 50, 160, and 300 bar. The expected peak horizontal acceleration in CU of Δσ = 160 bar is about 30 gals. Similar acceleration was recorded in CU during the 1985, Michoacan earthquake (M8.0). We compute expected ground motions at many sites in Mexico City using empirical transfer functions and random vibration theory and compare these motions and the expected damage in the city with those from the 1985 Michoacan earthquake. Results show that the overall expected damage during the postulated earthquake is ⅔ and 1⅓ of that during the Michoacan earthquake for Δσ = 160 and 300 bar, respectively. A greater percentage of low-rise construction, which constitute about 80% of the total in the city, will be damaged during the postulated earthquake than during the Michoacan earthquake. The expected ground motions for Δσ = 50 bar are smaller at all periods than those from the Michoacan earthquake. As the present building code for Mexico City contemplates coastal earthquakes of magnitude greater than 8.0, the case of Δσ = 50 bar is not of interest in this article. This preliminary study suggests a need for a more careful evaluation of expected ground motion in the Valley of Mexico from the postulated earthquake and its impact on the current design spectra of the city.