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LKAB’s underground mine in Kiirunavaara has experienced an increasing seismic activity the last ten years. This seismic activity is caused by the stress redistribution resulting from the mining method of large-scale sublevel caving. The energy from the seismic events propagate in the rock mass as seismic waves. If one of these waves interacts with an excavation, it will be subjected to dynamic loads, and damage can potentially occur. Damage can be caused by different mechanisms depending on many factors such as pre-existing structures in the rock mass and the state of stress. To prevent these damages, LKAB has installed a rock support system for handling dynamic loads. This thesis has analysed available damage mapping reports, investigations, pictures, seismic data and history, in order to evaluate the function of the support system when subjected to dynamic loads. The conclusion of the analysis is that the support system is well designed, but there are areas of improvement. The main damage mechanisms are bulking without ejection and rockfall due to seismic shaking. Bulking with ejection and ejection due to seismic energy transfer were concluded to not yet be a problem in the Kiirunavaara mine. This result implies that an improved stiffness, static strength and yieldability are to be considered in order to decrease the amount of bulking. For rockfall due to seismic shaking, there are two main areas of improvement. The structural mapping has to be given higher priority, and it should provide direct support recommendations if needed. The second part is to increase the static strength of the system in order to survive rockfall due to seismic shaking. Since bulking with ejection and ejection due to seismic energy transfer are not yet considered significant problems, there is no need to improve the support system with respect to absorption of kinetic energy. The location of the damages in the drift profiles were also analysed, and it was concluded that a majority of the damages that occurred in the footwall drifts were located in the corner of the abutment facing the orebody. In the crosscuts, a majority of the damages occurred in the abutment and roof. Based on this, it is suggested that the support should be improved in the abutment and roof of the crosscuts, and in the abutment facing the ore of the footwall drifts.

Thesis advisor: John E. Ebel / Thesis advisor: Mark D. Behn / On January 12, 2015, a magnitude 3.1 mainshock occurred in Plainfield, Connecticut near Wauregan Tilcon Quarry, causing modified Mercalli II-IV intensities. Shortly after the event, a team from Weston Observatory installed portable seismographs in the epicentral area. The portable array detected hundreds of small earthquakes from around the quarry, with 26 events that were accurately located. P-wave first motion directions obtained from readings of the mainshock suggest a thrusting focal mechanism on a NNE-SSW trending fault. In this research, we collected 113 gravity measurements in the proximity of the quarry to verify and correct local fault geometry proposed by historic aeromagnetic and geologic mapping. Interpretations of the computed simple Bouguer anomaly are consistent with historic mapping, with a few exceptions. The gravity survey constrains a NNE-SSW trending fault that dips west underneath the quarry, inferred to be the Lake Char-Honey Hill Fault, and reduces ambiguity in the position of an undefined ESE-WNW trending fault, which appears to be on strike to intersect the quarry. A 3D boundary element program (3D~Def) is used to simulate quarry-induced stress changes on these faults in order to analyze the possibility of inducing seismicity through crustal unloading in the region. Quarry operations resulted in the removal of mass from the crust, which decreased lithostatic load. In a setting confined by a maximum horizontal compressional stress, decreasing the lithostatic load, orminimum principal stress (σ3), shifts a Mohr-Coulomb diagram toward failure. The boundary element model shows that following the excavation of materials at the quarry, positive Coulomb failure stress changes occur on the west dipping Lake Char-Honey Hill Fault. In agreement with past studies, our results suggest that quarrying operations can trigger seismic activity in specific settings with stress regime, fault orientations, and rock characteristics such as those that exist in the northeastern U.S. In order to mitigate the risk for future earthquakes related to quarrying operations, these factors must be considered before operations begin. / Thesis (MS) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

The Creighton Mine is a structurally complex and seismically active mining environment. Microseismic activity occurs daily and increases with depth, complicating downward mine expansion. Larger magnitude events occur less frequently but can damage mine infrastructure, interrupt operations and threaten worker safety. This thesis explores the relationships between geological structure and mining-induced seismicity through geological, seismological and numerical modelling investigations in an area known as the Creighton Deep, with concentration on the 7400 Level (2255 m). Geological features within the Creighton Deep have a reported association with seismic activity. Four families of shear zones were identified during field investigations, the most prominent striking SW and steeply dipping NW. Seismicity from 2006-2007 is analyzed. Spatial and temporal trends and seismic event parameters show little correlation to shear zone geometry. Instead, seismic event parameters correlate to spatial clusters of events. A remote cluster of events to the southwest of the excavation exhibits anomalously high seismic parameter values. This area of the mine continues to be a source of elevated seismicity. Fault plane solutions are utilized to compare shear zone geometry with active slip surfaces. Solutions for macroseismic events are inconsistent, while microseismic event focal mechanisms have similar pressure, tension and null axes. The resulting solutions do not align with shear-zone orientations. A stress inversion using microseismic focal mechanism information yields a stress tensor that is comparable to the regional stress tensor. Universal Distinct Element Code numerical models demonstrate that a yield zone exists immediately surrounding the excavation. SW-striking shear zones modify the stress field, resulting in increased stress to the southeast of the excavation. These high-stress zones are areas of preferred seismic activity. Slip is induced on select SW-striking shear zones to the south of the excavation as well as localized yielding. The characteristics of mining-induced seismicity do not correlate to shear zones. Seismicity does compare to modelled stress: the yielded rock mass adjacent to the excavation has little seismicity; areas of high stress are areas of rock mass damage and dense seismic activity. It is thus proposed that seismicity in the Creighton Deep results from stress-induced rock mass degradation rather than fault-slip. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2009-09-11 10:35:17.525

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Human activities associated with the injection of fluids at depth are known to trigger earthquakes. Fluid injection increases the internal pore pressure of the host rock, which in turn reduces the effective stress and frictional resistance of faults that maintain the fractured rock system in a state of mechanical equilibrium. Under certain conditions, sufficiently high pore pressure can lower this frictional resistance below a critical threshold and initiate an earthquake – the relative motion of rock on either side of the fault plane. Many of these earthquakes are small and imperceptible without the aid of specialized instruments, but some may be large enough to pose a significant risk to life and property. Several emerging technologies that have the potential to shape the future of low-carbon energy production, including carbon capture and storage and enhanced geothermal energy production, are inextricably linked to large-scale injection of fluids into the subsurface. The risk of injection-induced earthquakes is a primary concern and potential barrier to widespread adoption of these technologies. New tools are required to help operators manage these risks and meet stakeholder expectations. Current knowledge enables operators to predict the conditions that would trigger such an earthquake, but few or no tools exist to predict the severity of the earthquakes, precluding a complete description of the risk associated with operating a large-scale injection well. This dissertation details the theoretical justification and initial validation of a methodology and software to simulate the motion of an earthquake as it occurs and quantify the severity in terms that are germane to experts in earthquake science. Specifically, this work utilizes the finite element method to solve the equations of motion dictated by the three-dimensional linear elastic constitutive equation. Novel aspects of this research include the treatment of friction at the fault interface as a constraint on the motion of the system, and the numerical methods necessary to solve this problem. This software was created exclusively with free and open source software, so that every aspect of its internal machinery may be scrutinized, replicated, and improved by future workers. / Doctor of Philosophy / Human activities associated with the injection of fluids at depth are known to trigger earthquakes. Many of these earthquakes are small and imperceptible without the aid of specialized instruments, but some may be large enough to pose a significant risk to life and property. Several emerging technologies that have the potential to shape the future of low-carbon energy production, including carbon capture and storage and enhanced geothermal energy production, are inextricably linked to large-scale injection of fluids into the subsurface. The risk of injection-induced earthquakes is a primary concern and potential barrier to widespread adoption of these technologies. New tools are required to help operators manage these risks and meet stakeholder expectations. Current knowledge enables operators to predict the conditions that would trigger such an earthquake, but few or no tools exist to predict the severity of the earthquakes, precluding a complete description of the risk associated with operating a large-scale injection well. This dissertation details the theoretical justification and initial validation of a methodology and software to simulate the motion of an earthquake as it occurs and quantify the severity in terms that are germane to experts in earthquake science. This software was created exclusively with free and open source software, so that every aspect of its internal machinery may be scrutinized, replicated, and improved by future workers.

The western margin of South America between 30ºS and 36ºS is seismically active. While the largest magnitude earthquakes are the interplate subduction zone events, the historically most devastating earthquakes have been the moderate-to-large magnitude earthquakes with depths < 35 km in the Andean back-arc. This region is characterized by accreted terranes later reactivated during Mesozoic extensional processes. Crustal seismicity in the back-arc is related to the thin-skinned Precordillera (PC) fold-thrust belt and the thick-skinned Sierras Pampeanas (SP) basement-cored uplifts overlying the flat slab segment. South of 33ºS, the active volcanic arc above the normally dipping subducted plate is also seismically active at crustal depths. In this study we combined historical and regional broadband seismic data to characterize moderate-to-large earthquakes and the crustal structure in this region. We have digitized and modeled teleseismic records of the 1944 and 1952 San Juan, Argentina PC earthquakes. Both events have shallow source depths, short duration of the source time functions with a thrusting focal solution for the 1944 (Mw 7.0) earthquake and a major strike-slip component in the 1952 (Mw 6.8) earthquake solution. By modeling regional broadband waveforms collected during the CHile-ARgentina Geophysical Experiment (CHARGE) during 2000 and 2002 we constrained the seismic moment tensor and improved focal depths for 27 crustal (3.5 < Mw < 5.1) earthquakes. We found predominantly thrust-fault focal mechanisms and focal depths of 10-26 km for earthquakes over the flat slab region; the eastern SP and active arc have earthquakes with strike-slip focal mechanisms and shallower depths. We used these same earthquakes to determine the crustal structure using raypaths that sample different geologic terranes. Our results indicate high Vp, low Vs for the northern Cordillera, PC and western SP thicker crust; low Vp, low Vs and a thinner crust beneath the arc (south of 33°S) consistent with a mafic composition and partial melt. The eastern SP basement shows low Vp, low Vs and thinner crust consistent with a more quartz-rich composition. These differences have an important control on the present day Andean earthquake deformation and the high seismic hazard posed in this region.

Architectural tectonics and the relationship of structural expression to ornament has been one of the oldest and most consistent themes in western architectural theory. For instance, the discussions of architectonics can be seen in the foundational literature from the Classical period, is present in Neo-classical architectural styles, in debates associated with modernist architecture, and in the latest digital interpretations of architecture. Tectonics and the idea that architecture ought to draw its aesthetic effects from its structural and material composition has, as a consequence, become a normative aspect of architectural theory and practice. Yet, in many situation cultural and geographical contexts this position does not have such a normative status. This thesis examines the legacy of this theme in architectural theory and practice in the particular cultural and geographical context of Japan and Taiwan. It focuses on the colonial cultural relationship between these countries, and to the West, as well as considering the seismic conditions that govern the culture of building around the Pacific West coast – the Ring of Fire. The argument that I will propose is that although the discussion of tectonics in westernised Japan has been scanty, the attitude and strategies the Japanese adopted for designing architecture and considering the relationship between structures and architectural surfaces can be framed differently. The difference between the traditional Japanese approaches to these questions and conventional Western considerations, is, in part, related to the significance of earthquakes to Japanese culture. The two traditions are not isolated. Japan was famously quick to adopt Western technologies and knowledge in the early twentieth century. In the context of architecture and building, this relationship produced a complex hybrid architectural culture in which the Japanese developed their own construction system and their attitude to the relationship between the structures and architectural surfaces. The thesis examines a further layer to this technological and cultural hybrid by examining the relationship between Japan and its colony Taiwan. The thesis argues that Japan’s relationship to the West, and its adoption and hybridization of architectural culture is evident in a complex way through their own colonial relationship to Taiwan. Through reviewing debates on structure and ornament in architecture in the Far East, the thesis adopts the concept of skeuomorph into this theoretical frame. Locating the concept of skeuomorph in this frame and interpreting the Japanese and Taiwanese cases by this concept allows us to reconsider the normative status of architectonic principles in architectural theory, and contribute to an understanding of colonial architectural history in the East Asia.

The wide application of fluid injection has caused a concern of the potential critical risk associated with induced seismicity. To help clarify the concern, this dissertation proposes a statistical approach for assessing seismic transitions associated with fluid injections by scientifically analyzing instrumental measures of seismic events. The assessment problem is challenging due to the uncertain effects of wastewater injections on regional seismicity, along with the limited availability of seismic and injection data. To overcome the challenge, three statistical methods are developed, with each being focused on a different aspect of the problem. Specifically, a statistical method is developed for early detection of induced seismicity, with the potential of allowing for site managers and regulators to act promptly and preparing communities for the increased seismic risk; the second method aims for addressing the further need of quantitatively assessing the transition of induced seismicity, which can reveal the underlying process of induced seismicity and provide data to support probabilistic seismic hazard analysis; and finally, the third method steps further to characterize the process of spatial distribution of induced seismicity, which accounts for spatial evolution of induced seismicity. All the proposed methods are built on the principles of Bayesian technique, which provides a flexible inference framework to incorporate domain expertise and data uncertainty. The effectiveness of the proposed methods is demonstrated using the earthquake dataset for the state of Oklahoma, which shows a promising result: the detection method is able to issue warning of induced seismicity well before the occurrence of severe consequences; the transition model provides a significantly better fit to the dataset than the classical model and sheds light on the underlying transition of induced seismicity in Oklahoma; and the spatio-temporal model provides a most comprehensive characterization of the dataset in terms of its spatial and temporal properties and is shown to have a much better short-term forecasting performance than the “naïve methods”. The proposed methods can be used in combination as a decision-making support tool to identify areas with increasing levels of seismic risk in a quantitative manner, supporting a comprehensive assessment to decide which risk-mitigation strategy should be recommended.