ΑΝΩΤΑΤΗ ΣΧΟΛΗ ΠΑΙ ΑΓΩΓΙΚΗΣ ΚΑΙ ΤΕΧΝΟΛΟΓΙΚΗΣ ΕΚΠΑΙ ΕΥΣΗΣ

ΑΝΩΤΑΤΗ ΣΧΟΛΗ ΠΑΙ ΑΓΩΓΙΚΗΣ ΚΑΙ ΤΕΧΝΟΛΟΓΙΚΗΣ ΕΚΠΑΙ ΕΥΣΗΣ (Α.Σ.ΠΑΙ.Τ.Ε.) Υποέργο: 5 Τίτλος: «Αρχιμήδης ΙΙΙ Ενίσχυση Ερευνητικών ομάδων στην Α.Σ.ΠΑΙ.Τ.Ε.» «ΣΥΓΚΡΙΤΙΚΗ ΑΞΙΟΛΟΓΗΣΗ ΑΠΟΤΕΛΕΣΜΑΤΩΝ ΕΠΙΦΑΝΕΙΑΚΩΝ ΜΕΘΟ ΩΝ ΕΠΙ ΤΟΠΟΥ ΠΡΟΣ ΙΟΡΙΣΜΟΥ ΥΝΑΜΙΚΩΝ Ι ΙΟΤΗΤΩΝ Ε ΑΦΙΚΩΝ ΣΧΗΜΑΤΙΣΜΩΝ ΣΕ ΘΕΣΕΙΣ ΚΑΤΑΓΡΑΦΗΣ ΣΕΙΣΜΙΚΩΝ ΓΕΓΟΝΟΤΩΝ ΚΑΙ ΑΞΙΟΠΟΙΗΣΗ ΑΥΤΩΝ ΣΤΟΝ ΠΡΟΣ ΙΟΡΙΣΜΟ ΣΧΕΣΕΩΝ ΕΞΑΣΘΕΝΙΣΗΣ» Επιστημονικός Υπεύθυνος: Π. Κ. ΠΕΛΕΚΗΣ ΠΑΡΑΔΟΤΕΟ ΕΠΙΣΤΗΜΟΝΙΚΗ ΕΡΓΑΣΙΑ ΣΕ ΔΙΕΘΝΕΣ ΕΠΙΣΤΗΜΟΝΙΚΟ ΣΥΝΕΔΡΙΟ «Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP)» Τίτλος Παραδοτέου: «Π4» Τίτλος επιστημονικής εργασίας : «SHEAR WAVE VELOCITY MEASUREMENTS IN THE AREA OF UNIVERSITY OF PATRAS ACCELEROGRAPH NETWORK (UPAN) USING ACTIVE & PASSIVE SURFACE WAVE METHODS» στο Πλαίσιο της Δράσης: 3, 4. Συντάκτες: 1. Vasileios S. Vlachakis, University of Patras, Greece 2. Panagiotis C. Pelekis, ASPETE, N. Heraklion, Greece 3. Anastasios V. Batilas, University of Patras, Greece (χωρίς αμοιβή) 4. George A. Athanasopoulos, University of Patras, Greece

Πίνακας περιεχομένων Σύντομη παρουσίαση της επιστημονικής εργασίας που παρουσιάστηκε στο συνέδριο... 2 Απόσπασμα προγράμματος συνεδρίου... 3 Η επιστημονική εργασία όπως δημοσιεύτηκε στα πρακτικά του συνεδρίου... 4 Διαφάνειες παρουσίασης... 9 1

Σύντομη παρουσίαση της επιστημονικής εργασίας που παρουσιάστηκε στο συνέδριο Η παρούσα εργασία παρουσιάσθηκε στο Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP) in Austin, Texas March 22-26, 215. Τίτλος εργασίας: SHEAR WAVE VELOCITY MEASUREMENTS IN THE AREA OF UNIVERSITY OF PATRAS ACCELEROGRAPH NETWORK (UPAN) USING ACTIVE & PASSIVE SURFACE WAVE METHODS ΠΕΡΙΛΗΨΗ Το Δίκτυο Επιταχυνσιογράφων του Εργαστηρίου Γεωτεχνικής Μηχανικής του Πανεπιστημίου Πατρών (UPAN) αποτελείται από οκτώ ψηφιακούς επιταχυνσιογράφους (ελευθέρου πεδίου) και μία κατακόρυφη διάταξη επιταχυνσιογράφων (μέχρι βάθος 72m από την επιφάνεια του εδάφους). Το δίκτυο καλύπτει το κεντρικό τμήμα της αστικής περιοχής της Πόλης των Πατρών (έκτασης 3km 2 ) και σύντομα θα επεκταθεί με την εγκατάσταση τεσσάρων νέων επιφανειακών επιταχυνσιογράφων. Στις θέσεις εγκατάστασης των επιταχυνσιογράφων, διεξήχθησαν μετρήσεις επιφανειακών κυμάτων για τον προσδιορισμό του προφίλ Vs βάθος ώστε τα δεδομένα αυτά να χρησιμοποιηθούν για το σχεδιασμό ενός τρισδιάστατου μοντέλου διακύμανσης της ταχύτητας Vs κάτω από την πόλη της Πάτρας και για τη διεξαγωγή αναλύσεων εδαφικής απόκρισης. Οι μετρήσεις επιφανειακών κυμάτων διεξήχθησαν χρησιμοποιώντας τις μεθόδους SASW και MASW, με χρήση ηλεκτρομηχανικών δονητών και πίπτων βάρος 25kg, αντίστοιχα. Επίσης, χρησιμοποιήθηκε η μέθοδος ReMi (Refraction Microtremor) η οποία εκμεταλλεύεται τον εδαφικό μικροθόρυβο, χρησιμοποιώντας την ίδια ευθύγραμμη διάταξη γεωφώνων που χρησιμοποιείται και για τις μετρήσεις με τη μέθοδο MASW. Συνδυάζοντας τα αποτελέσματα όλων των μετρήσεων (και ανάλογα με τη στάθμη θορύβου κάθε φορά), ήταν δυνατός ο προσδιορισμός του προφίλ Vs βάθος σε κάθε θέση του δικτύου επιταχυνσιογράφων UPAN, μέχρι μέγιστο βάθος περίπου 7m από την επιφάνεια του εδάφους. Προσδιορίστηκαν οι τιμές Vs,3 για κάθε θέση και χρησιμοποιήθηκαν για την κατάταξη του εδάφους σύμφωνα με την κατηγοριοποίηση του Ευρωκώδικα 8. Οι τιμές της ταχύτητας Vs,3 για τις θέσεις επιταχυνσιογράφων του αστικού δικτύου UPAN κυμάνθηκαν από 2/sec στην παραλιακή ζώνη της πόλης, έως 6m/sec σε απόσταση περίπου 3km από την ακτογραμμή. Η σύγκριση των μετρημένων τιμών Vs βάθος από τη μέθοδο επιφανειακών κυμάτων με αντίστοιχα αποτελέσματα από μετρήσεις Cross hole στη θέση της κατακόρυφης διάταξης επιταχυνσιογράφων έδειξε ικανοποιητική συμφωνία. Σύμφωνα με την κατηγοριοποίηση για το έδαφος του EC8, τέσσερεις από τις θέσεις του αστικού δικτύου UPAN κατατάσσονται στην κατηγορία Β, ενώ οι υπόλοιπες πέντε θέσεις κατατάσσονται στην κατηγορία C. 2

Απόσπασμα προγράμματος συνεδρίου 3

Η επιστημονική εργασία όπως δημοσιεύτηκε στα πρακτικά του συνεδρίου SHEAR WAVE VELOCITY MEASUREMENTS IN THE AREA OF UNIVERSITY OF PATRAS ACCELEROGRAPH NETWORK (UPAN) USING ACTIVE & PASSIVE SURFACE WAVE METHODS Vasileios S. Vlachakis, University of Patras, Greece Panagiotis C. Pelekis, ASPETE, N. Heraklion, Greece Anastasios V. Batilas, University of Patras, Greece George A. Athanasopoulos, University of Patras, Greece Abstract The University of Patras Accelerograph Network (UPAN) is comprised of eight free field digital accelerometers and a downhole array (to a depth of 72m) with one surface and three subsurface instruments. The network covers the central part of Patras urban area (3km 2 ) and is presently being expanded with four additional surface accelerometers. Shear wave velocity, Vs, measurements were performed at the locations of accelerographic stations and the derived Vs profiles are being used for establishing a 3-D Vs-depth model in the city area and for performing numerical analyses of ground motion amplification. Measurements of Vs vs. depth were performed by using the SASW and MASW techniques (employing electromechanical shakers and drop weights, respectively). The ReMi method was also employed by utilizing ambient noise recordings in the MASW receiver array. By combining the results of all measurements (and depending on noise level) it became possible to obtain Vs vs. depth profiles at each accelerographic station, to a depth of about 7m, from ground surface. Values of VS,3 were then estimated for each station and used for soil classification according to EC8. VS,3 values were found to range from 2m/sec at the coastal zone of the city to about 6m/sec at an inland distance of 3km. A comparison of Vs profiles measured at the location of downhole array by using both crosshole and surface wave techniques showed a very satisfactory agreement. According to EC8 four of the sites of UPAN are classified as ground type B, with the remaining five sites classified as ground type C. Introduction In the urban area of the city of Patras, Greece, an urban accelerographic network - called UPAN- has been installed, operated and maintained by the Geotechnical Engineering Laboratory of the Dept. of Civil Engineering of the University of Patras. The operation of UPAN, started in 26 and it is presently comprised of 8 free-field surface accelerometers and one downhole array. The locations of UPAN accelerographic stations are shown in Fig. 1, whereas the corresponding coordinates are given in Table 1. The aim of the present research is the performance of ground response analyses at each accelerographic station and the study of ground amplification. To achieve the above objective, it is necessary to know the Vs vs. depth profiles at the location of each station. Surface wave measurements were conducted to obtain the required Vs profiles. Additional 4

measurements are also being conducted at interstation locations to densify the grid of available data and be able to generate a 3-D model. Vs - depth Measurements Four different methods were used to perform Vs-depth measurements in the urban area of Patras. The methods were combined in such a way as to utilize only the advantages of each method: (a) the SASW method was used utilizing a pair of electromechanical shakers (Thompson et al, 27). By utilizing the swept sine method, and using a dynamic signal analyzer (with appropriate band pass filters), it became possible to record the vibration amplitudes of the receivers in the frequency domain. The harmonic waves are recorded by using a pair of geophones in a linear array and at distances of up to 6m from the source, depending on the noise of each site (b) the SASW and MASW method were used, utilizing a drop weight of 25kg as a source in relatively quiet sites (Pelekis and Athanasopoulos, 211). For the signal recording a set of 12 or 24 geophones were used in a linear array, (c) the ReMi method (Louie, 21) was used in the noisy environment of the city center, by applying a linear array of 12 or 24 geophones, as in the SASW and MASW method. Dispersion curves obtained from field data were inverted by using the SIM method (Pelekis and Athanasopoulos, 211). In each site, the final dispersion curve used for inversion was determined by combining the SASW dispersion curve for the upper 3 to 4m and the ReMi dispersion curve for the deeper soil zone, reaching in some cases depths up to 8m. Figure 1: Satellite image (Google Earth ) of the urban area of Patras, Greece, with the locations of the 8 free field accelerographs (UP-1 to UP-8) and the downhole array (VA-1). 5

Table 1: Coordinates of the UPAN accelerographic stations, in the city of Patras. Accelerographic Station Lat ( ) Lon ( ) UP-1 38.269413 21.747824 UP-2 38.25935 21.766697 UP-3 38.24928 21.747861 UP-4 38.22838 21.7284 UP-5 38.219584 21.7423 UP-6 38.21493 21.76189 UP-7 38.24927 21.7351 UP-8 38.234736 21.747275 VA-1 38.232413 21.74179 Results of Measurements Vs vs. depth profiles for each accelerographic station (using a common scale) are shown in the diagrams of Fig. 2. The Vs profiles for the free field stations UP-1 and UP-3 to UP-8 were derived from the data of SASW method (using a pair of electromechanical shakers and making use of the swept sine method), whereas the profile at UP-2 station and the VA-1 site, derived by combining the results of all SASW and ReMi methods. Particularly, at VA-1 site, the final Vs profile was derived by combining all the applied surface waves methods and comparing the results with data obtained from cross-hole measurements. As it can be seen from the relevant diagram (in which cross hole measurements results are also shown) the comparison is very satisfactory (weighted average deviation 2%). In this particular site, the results of measurements were also compared successfully to results obtained by cross correlating weak earthquake signals recorded at different depths in the downhole array VA-1. The details of all the comparisons between different surface wave methods used in the present research, will be the topic of a future article. Conclusions Surface wave measurements at the location of 8 free field accelerometers and one downhole array were performed, in the area of UPAN. The results of measurements in terms of Vs vs. depth profile, led to the determination of VS,3 value and profile up to about 8m depth. The VS,3 values, ranging from 23m/sec up to 57m/sec, classify the examined accelerometer stations of UPAN, to Ground Type B (36-8m/sec) and Ground Type C (18-36m/sec), according to Eurocode 8. ACKNOWLEDGEMENTS This research has been co-financed by the European Union (European Social Fund ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding 6

Program: ARCHIMIDIS III: Research Teams Reinforcement in ASPETE (MIS:383576) of the Operational Program "Education and Lifelong Learning. References European Standard EN 1998-1 (24), Eurocode 8: Design of Structures for Earthquake Resistance, Part 1: General Rules, Seismic Actions and Rules for Buildings, EN 1998-1 : 24, November 24. Louie, J. N. (21), Faster, Better: Shear-wave Velocity to 1 Meter Depth From Refraction Microtremors Arrays: Bull. Seism. Soc. Am., 91, 347-364. Pelekis, P C. and Athanasopoulos, G. A., (211), An Overview of Surface Wave Methods and a Reliability Study of a Simplified Inversion Technique, Soil Dynamics and Earthquake Engineering, 31, 1654-1668. Thompson, E. M., Baise, L. G. and Kayen, R. E. (27), Spatial Correlation of Shear-Wave Velocity in the San Francisco Bay Area Sediments, Soil Dynamics and Earthquake Engineering, 27, 144-152. 7

2 4 6 8 1 12 1 Shear wave velocity, V S (m/sec) UP-1 Shear wave velocity, V S (m/sec) 2 4 6 8 1 12 1 UP-2 1 Shear wave velocity, V S (m/sec) 2 4 6 8 1 12 UP-3 2 2 2 3 3 3 4 5 4 5 4 5 6 6 6 7 V S,3 =38m/sec 8 2 4 6 8 1 12 1 UP-4 7 V S,3 =316m/sec 8 2 4 6 8 1 12 1 UP-5 7 V S,3 =422m/sec 8 2 4 6 8 1 12 1 UP-6 2 2 2 3 3 3 4 5 4 5 4 5 6 6 6 7 8 V S,3 =23m/sec 2 4 6 8 1 12 1 UP-7 7 8 V S,3 =57m/sec 2 4 6 8 1 12 1 UP-8 7 8 V S,3 =556m/sec 2 4 6 8 1 12 VA-1 1 2 2 2 3 4 5 3 4 5 3 4 5 6 6 6 7 8 V S,3 =2m/sec 7 8 V S,3 =345m/sec 7 8 V S,3 =291m/sec Surface Waves Cross Hole Figure 2: VS vs. depth profiles for the 8 free field accelerographic stations and the downhole array, comprising the UPAN, Patras, Greece. 8

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