A study was undertaken to evaluate an automated process to invert for seismic moment tensors from seismic data recorded in mining environments. The data for this study was recorded at Nickel Rim South mine, Sudbury, Ontario. The mine has a seismic monitoring system manufactured by ESG Solutions that performs continuous monitoring of seismicity. On average, approximately 400 seismic events are recorded each day. Currently, data are automatically processed by ESG Solution's software suite during acquisition. The automatic processors pick the P- and/or S-wave arrivals, locate the events and solve for certain source parameters, excluding the seismic moment tensor. In order to solve for the moment tensor, data must be manually processed, which is laborious and therefore seldom performed. This research evaluates an automatic seismic moment tensor inversion method and demonstrates some of the difficulties (through inversions of real and synthetic seismic data) of the inversion process. Results using the method are also compared to the inversion method currently available from ESG Solutions, which requires the manual picking of first-motion polarities for every event. As a result of the extensive synthetic testing of the automatic inversion program, as well as the inversion of real seismic data, it is apparent that there are key parameters requiring greater accuracy in order to increase the reliability of the automation. These parameters include the source time function definition, source location (in turn requiring more accurate and precise knowledge of the earth media), arrival time picks and an attenuation model to account for ray-path dependent filtering of the source time function. In order to improve the automatic method three key pieces of research are needed: (1) studying various location algorithms (and the effects of increasing earth model intricacy) and automatic time picking to improve source location methods, (2) studying how the source time pulse can be accurately extracted from the seismic records, as well as the validity of various source models, and (3) studying how attenuation can be modeled more accurately to account for the filtering of the seismic waves through the earth media (in particular distortion to the source time function). / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2012-08-17 23:08:32.198

Acoustic emissions (AEs) are generated as a result of the creation of, or movement on microcracks in a rock mass. Hypocentres of AEs have been used as a very effective method of visualising the extent (amount and location) of microcrack damage. Studies have used AE locations to investigate both the behaviour of rock failure in laboratory experiments, and to evaluate damage in the Excavation Disturbed Zone (EDZ) around underground openings. The latter has particular significance for the safe storage of nuclear materials in deep underground facilities. Because AEs represent phenomena associated directly with the physical processes occurring in microcracking, then they can also be used to evaluate the fundamental mechanics of the failure. In this thesis a moment tensor (MT) inversion procedure is developed for AEs. This utilises full-waveform records from an array of ultrasonic piezoelectric transducers distributed around the rock mass. The procedure is tested using synthetic amplitudes and is shown to be robust even with high amplitude uncertainties. The inversion is particularly good at resolving the volumetric component in the source. The procedure allows a precise and well-constrained analysis of the forces that are creating the AEs, and, in some cases, that are actually creating the damage. The mechanics can then be related to the stress field in the rock mass, or can be compared to results from dynamic micromechanical models. Three case studies are performed. Two of these investigate the fundamental behaviour of microcracking in the laboratory. A series of laboratory tests are conducted using polyaxial stress to study the mechanics of damage under realistic in situ stress paths. The third case study investigates the mechanics of failure operating in the EDZ. AEs are shown to be truly scaled earthquakes although with often-complex non-double-couple mechanisms.

Der Elburs im Norden Irans ist ein durch die Konvergenz der Arabischen und Eurasischen Platte verursachtes doppelt konvergentes Gebirge. Das komplexe System von Blattverschiebungen und Überschiebungen sowie die Aufnahme der Deformation im Elburs ist noch nicht sehr gut verstanden. Eine neu zu entwicklende Methode zur Inversion von seismischen Momententensoren, die unterschiedliche Beobachtungen verschiedener Stationstypen kombiniert invertiert, soll die bisher hauptsächlich strukturelle/geomorphologische Datengrundlage um Momententensoren auch kleinerer Magnituden (M < 4.5) erweitern. Dies ist die notwendige Grundlage für detaillierte seismotektonische Studien, die wiederum die Basis für seismische Gefährdungsanalysen bilden.

This thesis examines the role of Acoustic Emission (AE) as a non-destructive testing technique for concrete structures. The work focuses on the development of experimental techniques and data analysis methods for the detection, location and assessment of AE from the failure of plain and reinforced concrete specimens. Four key topics are investigated:

3 Title: Moment-tensor inversion of earthquakes in Greece, method ISOLA Author: Dana Červinková Department: Department of Geophysics Supervisor: Prof. RNDr. Jiří Zahradník, DrSc. Supervisor's e-mail address: jz@karel.troja.mff.cuni.cz Abstract: The possibility of obtaining a reliable moment tensor using a low-frequency waveform inversion from a single seismic station is studied. Deviatoric part of the moment tensor is described in usual way, using its orientation (angles strike, dip, rake), scalar seismic moment M0 and the double-couple percentage (DC%), and also by means of the coefficients of linear combination of elementary mechanisms. We estimate the formal error of the coefficients and study conditionality of the inverse problem. Data from earthquakes Trichonis (Mw = 5.2, April 2007) and Leonidio (Mw = 6.2, January 2008), Greece, are processed using software ISOLA (Sokos and Zahradník). The moment tensor is calculated from many stations and its stability is tested. This reference solution is compared to those independently obtained from single stations. Synthetic tests are performed to understand why the single-station estimates are sufficient for Trichonis, but not for Leonidio, paying attention to the focal depth, station azimuth and epicentral distance. It is found that the depth is crucial at...

Earthquake swarms occur frequently in West Bohemia, Central Europe. Their occurrence is correlated with and propably triggered by fluids that escape on the earth's surface near the epicentres. These fluids raise up periodically from a seemingbly deep-seated source in the upper mantle. Moment tensors for swarm events in 1997 indicate tensile faulting. However, they were determined under assumption of seismic isotropy although anisotropy can be observed. Anisotropy may obscure moment tensors and their interpretation. In 2000, more than 10,000 swarm earthquakes occurred near Novy Kostel, West Bohemia. Event triggering by fluid injection is likely. Activity lasted from 28/08 until 31/12/00 (9 phases) with maximum ML=3.2. High quality P-wave seismograms were used to retrieve the source mechanisms for 112 events between 28/08/00 and 30/10/00 using > 20 stations. We determine the source geometry using a new algorithm and different velocity models including anisotropy. From inversions of P waves we observe ML<3.2, strike-slip events on steep N-S oriented faults with additional normal or reverse components. Tensile components seem to be evident for more than 60% of the processed swarm events in West Bohemia during the phases 1-7. Being most significant at great depths and at phases 1-4 during the swarm they are time and location dependent. Although tensile components are reduced when anisotropy is assumed they persist and seem to be important. They can be explained by pore-pressure changes due to the injection of fluids that raise up. Our findings agree with other observations e.g. correlation of fluid transport and seismicity, variations in b-value, forcing rate, and in pore pressure diffusion. Tests of our results show their significance.

The complex system of strike-slip and thrust faults in the Alborz Mountains, Northern Iran, are not well understood yet. Mainly structural and geomorphic data are available so far. As a more extensive base for seismotectonic studies and seismic hazard analysis we plan to do a comprehensive seismic moment tensor study also from smaller magnitudes (M < 4.5) by developing a new algorithm. Here, we present first preliminary results.

Στην παρούσα εργασία υπολογίστηκαν μηχανισμοί γένεσης σεισμών, χρησιμοποιώντας ένα μικροσεισμικό δίκτυο, εγκατεστημένο στη νότια Αλβανία. Πρόκειται για μια περιοχή που βρίσκεται στο νοτιοδυτικό άκρο της Αλβανίας, κοντά στα σύνορα με την Ελλάδα και γεωλογικά ανήκει στην Ιόνια ζώνη. Συγκεκριμένα μελετήθηκαν και επεξεργάστηκαν 22 σεισμικά γεγονότα που επιλέχθηκαν με συγκεκριμένα κριτήρια, από το σύνολο των καταγραφών του μικροσεισμικού δικτύου που είχε εγκατασταθεί στην περιοχή. Το μικροσεισμικό δίκτυο τοποθετήθηκε στηνπεριοχή του αντικλίνου Kurveleshi. Η δομή του (ALIAJ et al. 1991) αποδίδεται σε τεκτονικά ρήγματα κατά μήκος και εγκαρσίως σε αυτό. Ο ρόλος της λιθολογίας στο σχηματισμό του αντικλίνου είναι σημαντικός γιατί πάνω στις μεγάλες επωθήσεις αναπτύσσονται διαπυρικοί δόμοι. Εφαρμόστηκαν τρεις μέθοδοι υπολογισμού των μηχανισμών γένεσης: α) Προσδιορισμός των μηχανισμών γένεσης με χρήση δεδομένων πολικότητας-πρόγραμμα FPFIT, β) Προσδιορισμός των μηχανισμών γένεσης με αντιστροφή κυματομορφών-πρόγραμμα ISOLA και γ) Προσδιορισμός των μηχανισμών γένεσης με χρήση πλατών κυμάτων Ρ, SV και SH – πρόγραμμα FOCMEC. Αρχικά εφαρμόστηκε η μέθοδος των πρώτων αποκλίσεων των P κυμάτων που χρησιμοποιείται από τους σεισμολόγους εδώ και πολλά χρόνια για την εύρεση του μηχανισμού γένεσης ενός σεισμού δίνοντας έτσι τα χαρακτηριστικά των δύο επιπέδων διάρρηξης. Αυτή η μέθοδος βασίζεται στο γεγονός ότι ο τρόπος ακτινοβολίας των σεισμικών κυμάτων έχει άμεση σχέση με τη γεωμετρία του ρήγματος. Το κύμα P είναι το πρώτο κύμα που καταγράφεται μετά από έναν σεισμό στα όργανα στους σταθμούς καταγραφής και ως εκ τούτου είναι μια φάση πολύ εύκολα αναγνωρίσιμη. Η βασική ιδέα για την εφαρμογή της μεθόδου είναι ότι η πρώτη κίνηση των επιμήκων κυμάτων, δηλαδή εάν είναι αραίωση (άφιξη με φορά προς τα κάτω) ή συμπίεση (άφιξη με φορά προς τα πάνω) εξαρτάται από τη διεύθυνση (το αζιμούθιο) του σταθμού καταγραφής σε σχέση με το σεισμό. Με τη συγκεκριμένη μέθοδο προσδιορίστηκαν οι μηχανισμοί γένεσης και για τα 22 σεισμικά γεγονότα. Υπάρχει όμως και η περίπτωση όπου μια πρώτη άφιξη δεν είναι σαφής ως προς το εάν παριστάνει μια αραίωση ή συμπίεση και δυσχερένει την ακριβή χάραξη των δυο επιπέδων. Αυτό μπορεί να συμβαίνει είτε λόγω του θορύβου, είτε γιατί η πρώτη άφιξη είναι πολύ μικρή σε πλάτος οπότε και πολύ δύσκολα αναγνωρίσιμη. Αυτές λοιπόν οι δυσκολίες μπορεί να μην επιτρέπουν τον ακριβή προσδιορισμό του μηχανισμού γένεσης, γι αυτό σε μια δεύτερη φάση χρησιμοποιήθηκαν και τα πλάτη των κυμάτων. Συγκεκριμένα αυτή η μέθοδος περιλαμβάνει εκτός των φάσεων των πρώτων αποκλίσεων και το λόγο των πλατών των εγκαρσίων κυμάτων S, ως προς το πλάτος των επιμήκων κυμάτων Ρ, δηλαδή το λόγο S/P των κυμάτων βελτιώνοντας αισθητά τα αποτελέσματα όπου υπάρχουν λίγοι σταθμοί ή δεν είναι καλά κατανεμημένοι αζιμουθιακά. Η μέθοδος αυτή θεωρείται σχετικά απλή καθώς απαιτούνται μόνο οι διαφορές μεταξύ της διαφορετικής απόσβεσης των κυμάτων P και S ενώ ενδιαφέρουν και όποιες τοπικές επιδράσεις υπάρχουν σε κάθε σταθμό (site effect) που μπορούν να επηρεάσουν τα πλάτη. Με τη συγκεκριμένη μέθοδο προσδιορίστηκαν οι μηχανισμοί γένεσης για τα 21 σεισμικά γεγονότα. Η τελευταία μέθοδος επεξεργασίας που χρησιμοποήθηκε, περιλαμβάνει τον υπολογισμό μηχανισμών γένεσης με τη χρήση του προγράμματος ISOLA το οποίο προσδιορίζει τον τανυστή της σεισμικής ροπής με αντιστροφή κυματομορφών και για δεδομένα τοπικών σεισμών. Με τη συγκεκριμένη μέθοδο προσδιορίστηκαν οι μηχανισμοί γένεσης για τα 12 σεισμικά γεγονότα. Η διαδικασία της αντιστροφής του τανυστή της σεισμικής ροπής παρέχει αξιόπιστες πληροφορίες σχετικά με τον μηχανισμό γένεσης και ειδικότερα τη γεωμετρία της διάρρηξης στο χώρο, τη σεισμική ροπή, το μέγεθος σεισμικής ροπής Mw, τη σεισμική πηγή και το βάθος της εστίας. Αποτελεί γενικά ένα μαθηματικό πρόβλημα που λύνεται συγκρίνοντας τις παρατηρούμενες κυματομορφές με τα αντίστοιχα συνθετικά κύματα. Το πρόβλημα επιλύεται ελαχιστοποιώντας τις διαφορές μεταξύ των συνθετικών και των παρατηρούμενων κυματομορφών. Από τη μελέτη και την επεξεργασία των μικροσεισμικών δεδομένων στη νότια Αλβανία προκύπτει ότι είναι μια περιοχή με έντονη μικροσεισμική δραστηριότητα Οι μηχανισμοί γένεσης που υπολογίστηκαν συμφωνούν μεταξύ τους και για τις τρεις μεθόδους που εφαρμόστηκαν ( FPFIT, ISOLA, FOCMEC). Συγκεκριμένα υπολογίστηκαν ανάστροφα και οριζόντια ρήγματα που επιβεβαιώνουν το καθεστώς συμπίεσης που επικρατεί στην περιοχή. Η σύγκρουση του ανώτερου μανδύα της αδριατικής μικροπλάκας με το αλβανικό ορογενές προτείνεται για να εξηγήσει τους μηχανισμούς γένεσης που παρατηρήθηκαν. Επίσης προσδιορίστηκαν και μηχανισμοί κανονικών ρηγμάτων που προέρχονται όμως από μικρούς σεισμούς και δικαιολογούνται από την εμφάνιση εβαποριτών στην περιοχή μελέτης. Τέλος διαπιστώθηκε ότι είναι εφικτός ο υπολογισμός των μηχανισμών γένεσης με αντιστροφή κυματομορφών ακόμα και για μικρά σεισμικά γεγονότα. Με απαραίτητες όμως προυποθέσεις η αντιστροφή να γίνεται χρησιμοποιώντας υψηλές συχνότητες κι επίσης να υπάρχουν: σταθμοί σε κοντινή απόσταση (4km περίπου), καλό μοντέλο ταχυτήτων και καλή ποιότητα καταγραφών. / In the present work were calculated tensor solutions of earthquakes, using a microseismic network, located in Southern Albania. This is an area located at the southwestern tip of Albania, near the border with Greece and geologically belongs to the Ionian Zone. Specifically, they had studied and worked 22 seismic events were selected by specific tests from all the records of microseismic network was installed in the area. They had applied three methods for calculating focal mechanisms: a) Identification of mechanisms using polarity data – program FPFIT, b) Determination of focal mechanisms with reverse  waveform – program ISOLA and c) Determination of focal mechanisms using P wave amplitudes, SV and SH – program FOCMEC. Initially, was being  used the methodology of the first differences of P waves. This method relies on the fact that the way radiation of seismic waves is directly related to the geometry of the fault. The basic idea of the method is that the first motion of long waves, ie if dilution (arrival by pointing down) or compression (arrival by pointing up), depends on the direction (azimuth) of the station registration in relation to the earthquake. With this method were determined tensor solutions for the 22 seismic events. In a second step was being used and the amplitudes of seismic waves. Specifically, this method include other steps of the first gap and the reason of the amplitudes of transverse waves S, for amplitudes of waves P, ie the reason S/P waves significantly improved results with few or no stations are well distributed azimuthal. This method is relatively simple and requires only the differences between the different damping of the waves P and S and interest any local effects in each station (site effect) that can affect the back. By this method were also determined tensor solutions for 21 seismic events. The last method of treatment was used, includes calculation of focal mechanisms using the ISOLA project that identifies seismic moments tensor inversion of waveform data and local earthquakes. We were determined tensor solutions for 12 seismic events. The reversal process of the seismic moment tensor provides reliable information about the mechanism of generation and in particular the geometry of the fracture site, the seismic moment, the magnitude of seismic moment Mw, the seismic source and the depth of the outbreak. By the study and treatment of microseismic data in south Albania result that is an area of intense microseismic activity. The tensor solutions calculated, agree with each other for all three methods applied (FPFIT, ISOLA, FOCMEC). Specifically, calculated and horizontal reverse faults confirm the compression scheme that prevails in the region. Also identified mechanisms of normal faults that come from small earthquakes as justified by the appearance of evaporates in the study area. Finally, had found that is feasible the calculations of focal mechanisms with reverse waveforms even small seismic events.

Title: The source process of Greek earthquakes Author: Dana K ížová Department: Department of Geophysics Supervisor of the doctoral thesis: Prof. RNDr. Ji í Zahradník DrSc., Department of Geophysics Abstract: Investigations of moment tensor (MT) and its uncertainty are topical. This thesis is focused on isotropic component of three shallow earthquakes: Event A in Cretan Sea (Mw 5.3) and two events near Santorini island, B (Mw 4.9) and C (Mw 4.7). MT is inverted from full waveforms in an assumed 1D velocity model. The inverse problem is non-linear in centroid depth and time, and linear in six MT parameters, one is the MT-trace. Uncertainty of isotropic component is studied by a new approach (K ížová et al., 2013). The trace is systematically varied, and remaining parameters are optimized. The method reveals tradeoffs between the isotropic component, depth, time, and focal mechanism. From two existing velocity models, we prefer the one with lower condition number, in which a (positive) isotropic component is indicated for event B. To rapidly assess a likely existence of isotropic component, an empirical method is proposed (K ížová et al., 2016). It is based on comparison between depth- dependences of waveform correlation in full and deviatoric modes. Based on extensive synthetic tests, the method confirms a...

Presented in this thesis are some basic concepts and applications of seismic hazard analysis and the elements that influence the amplitude and geometric attenuation of earthquake ground motion. This thesis centers on the identification of the styles of failure, focal mechanisms, and the state of regional stress in the study area. Seismic hazard is a complex problem often involving considerable uncertainties. Therefore it is reasonable to consider different seismic hazard analysis approaches in order to as robustly as possible define zones of different levels of hazard. With the aim of characterizing and quantifying hazard in the east African region of Eritrea and its surroundings, a study is included in the thesis presenting hazard maps constructed using two non-parametric probabilistic seismic hazard analysis (PSHA) approaches. Peak ground acceleration (PGA) values for 10% probability of exceedence in 50 years are computed at given grid points for the whole selected area and results from both methods are compared. Other aspects addressed in the thesis include the determination of source parameters of selected earthquakes that occur in the Afar region. The styles of faulting, the mechanisms involved during the rupture process and the states of stress along the major tectonic features are also highlighted. Source parameters for selected events in the region were re-evaluated and improved solutions obtained. An aftershock sequence in the Hengill volcanic area in SW Iceland, following the major event that occurred on June 4, 1998, was used to investigate improved methodologies for moment tensor using a relative approach. The sensitive and spatially dense seismic network in this area reveals large sets of clustered events allowing the power of the new methodology to be demonstrated and providing greater insight into the tectonic implications of the activity in the area.