Archaeoseismology and Palaeoseismology in the Alpine ... - Tierra

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Prior to the present study all evidence of non‐seismic activity, which could affect results, had to be discounted. Intensive study of the paleoclimate, the geology of the cave and its hyrdrogeological setting, allowed us to exclude evidence for damage from numerous sources. They include anthropogenic activity, ice creep, underground glaciers, frost action, erosion, soil creep, effects of water circulation, flooding, debris flow, incations caused by non‐earthquake related activity and slope movements (Becker et al., 2006). The cave is ca. 50m2 in area and divided into two chambers. In an upper chamber speleothems are abundant. For this chamber a plan was made in order to document sample location (Fig. 3A). Throughout this chamber evidence of collapses is visible in broken speleothems (Fig. 3B), fallen stones and a fallen segment of its wall. In the lower chamber chalk and cherts are exposed, while only few speleothems are found, and those are predominantly below cracks (Fig. 3C). DATING OF BROKEN SPELEOTHEMS Broken speleothem samples were collected from all parts of the upper chamber of the cave (yellow markers in Fig. 3). The samples consist of broken stalagmites and stalactites and flowstone cores drilled from the cave floor exposing fallen and embedded speleothems. For each seismite sample a seismic contact (i.e. the precise location at which the laminae of the speleothems are broken. See Fig. 4) was established and the closest laminae to each contact were sampled with a small drill. The last lamina which grew before the break event was termed a pre‐ seismic sample, while the first one to grow after the break event was termed a post‐seismic sample (Fig. 4). In this study, dating with the U‐Th method was conducted on the Multiple Collector Inductively Coupled Plasma Mass Spectrometer (MC‐ICP‐MS) at the Geological Survey of Israel. The MC‐ICP‐MS produces high analytical precision results and enables work on small samples (ca. 0.3g) that, due to an ability to sample individual laminae, give ages at high resolutions. The ages found for Denya Cave were calculated as single samples using the age equation according to Broecker and Kaufman (1965). Ages determined for seismite samples were seen to form clusters at very specific time intervals. Since some samples had high detrital content, their ages had to be corrected (Kaufman et al., 1998). In order to correct for detrital Th, the samples were divided according to the age groupings and plotted on a three dimensional isochron where x=230Th/238U, y=234U/238U and z=232Th/238U (Ludwig and Titterington, 1994), using the Isoplot3.7 program. Ongoing research indicates that those clusters, when falling on a reasonably accurate three dimensional isochron plot, are considered to be groupings of a single age indicating one seismic event. RESULTS A total of 68 speleothem samples was taken and inspected from Denya Cave, 32 of which were broken and thus, identified as likely to indicate seismic activity. Some of those samples had more than one seismite (i.e. a record of a single seismic event). The ages obtained from 1 st INQUA‐IGCP‐567 International Workshop on Earthquake Archaeology and Palaeoseismology 18 those seismites vary greatly. They indicate seismic activity during the last 350 ka; older samples are in secular equilibrium and cannot be further dated. A seismic event is associated with the age clusters, but only when seismites appear to be sound indicators of a physical break in the speleothems examined and when there are pre‐ and post‐seismic event samples in the same cluster. Results further show that during the last 80 ka at least five seismic events occurred, causing damage to speleothems in Denya cave (~11, 22, 28, 37 and 55 ka). Indicators for an event at ~5 ka were also found, but they are not strongly substantiated by the types of seismites representing them. Indicators for older events that affected the cave were found, but due to the relatively large error on these ages, we could not identify clusters. CONCLUSIONS Fig. 4: A seismite from Denya Cave, sample DN‐7 The dating of speleothems using the U‐Th method, combined with their subsequent correction for detrital Th, employing the three dimensional isochron plots, represents a new approach to identifying seismic events in the Quaternary. This research in Denya Cave, Mt Carmel, Haifa, indicates that speleothems there recorded five seismic events that caused damage to the cave during the last 80 ka. The latest such event occurred between 11 and 10 ka. Yet another, younger event, at ~5 ka may also have taken place, but additional evidence is necessary to validate that observation. Acknowledgements: This research was funded by the Israel Science Foundation, Grant no. 1006/2004 to A. Agnon. The authors wish to thank M. Stein, G. Hartman, A. Vaks, and T. Zilberman for useful discussions. All the staff of the Geological Survey of Israel who helped with all technical matters: S. Ashkenazi, Y. Mizrachi, C. Hemo, N. Tapliakov, I. Segal and O. Yoffe. L. Magagritz, M. Laskow, E. Braun, M. Kanari, U. Ryb for
continuous support. N. Shalev, G. Gerber, Y. Burstein, N. Shcheny, Y. Noymaer, E. Merder have contributed labour and effort to the success of this research. References Agnon, A., Migowski, C., Marco, S., (2006), Intraclast breccias in laminated sequences reviewed: Recorders of paleo‐ earthquakes. Special Paper‐ Geo. S. of A., 401, 195‐214. New frontiers in Dead Sea paleoenvironmental research. Amiran, D.H.K., Arieh, E. and Turcotte, T. (1994), Earthquakes in Israel and Adjacent Areas: Macroseismic Observations since 100 B.C.E. Israel Explor. Jour. 44, 260‐305. Becker, A., Davenport, C.A., Eichenberger, U., Gilli, E., Jeannin, P.Y. and Lacave, C. (2006), Speleosismology: A critical perspective. J. Seismol. 10, 371‐388. Becker, A., Ferry, M., Moneck, K., Schnellmann, M. and Giardini, D. (2005), Multiarchive paleoseismic record of late Pleistocene and Holocene strong earthquakes in Switzerland. Tectonophys. 400, 153‐177. Begin, Z.B., Steinberg, D.M., Ichinose, G.A. and Marco, S. (2005), A 40,000yr unchanging seismic regime in the Dead Sea rift. Geology, 33, 257‐260. Broecker, W.S. and Kaufman, A., (1965) Radiocarbon chronology of Lake Lahontan and Lake Bonneville II, Great Basin, Geol. Soc. Amer. Bull. 76, 537–566. Davenport, C.A., (1998), Karst as a record of Paleoseismicity. Y. Quinif (Ed), Karst and Tectonics. Contributions to the international symposium on Karst and Tectonics. Relations between Tectonics, Karst and Earthquakes, Speleochrons hors‐ serie, pp. 41‐44. Ellenblum, R., Marco, S., Agnon, A., Rockwell, T. and Boas, A., (1998), A crusader castle torn apart by the earthquake of dawn, 20 May 1202. Geology, 26, 303‐306. Enzel, Y., Kadan, G. and Eyal, Y., (2000), Holocene earthquakes inferred from a fan delta sequence in the Dead Sea graben. Quat. Res. 53, 1, 34‐48. 1 st INQUA‐IGCP‐567 International Workshop on Earthquake Archaeology and Palaeoseismology 19 Hofstetter, A., Ron, H., and van Eck, T., (1989), Mt. Carmel Earthquake Sequence. Seismol. Div. Inst. Petrol. Res. Geophys, Holon, Israel 303/1829/88 (1). Hofstetter, A., van Eck, T. and Shapira, A., (1996), Seismic activity along fault branches of the Dead Sea‐Jordan transform system: The Carmel‐Tirza Fault system. Tectonophys. 267, 317‐330. Kaufman, A., Wasserburg, G.J., Porcelli, D., Bar‐Matthews, M., Ayalon, A. and Halitcz, L. (1998), U‐Th isotope systematics from the Soreq Cave, Israel and climatic correlations. Earth and Planetary Sci. Let., 156, 141‐155. Kagan, E.J., Agnon, A., Bar‐Matthews, M. and Ayalon, A., (2005), Dating large infrequent earthquakes by damaged cave deposits. Geology, 33, (4), 261‐264. Lacave, C. Koller, M.G. and Eozcue, J.J. (2004), What can be concluded about seismic history from broken speleothems? J. Earthquake Engineering, 8(3), 431‐455. Maryline Le Beon, Yann Klinger, Abdel Qader Amrat, Amotz Agnon, Louis Dorbath, Gidon Baer, Jean‐Claude Ruegg, Olivier Charade and Omar Mayyas, (2008), Slip rate and locking depth from GPS profiles across the southern Dead Sea Transform. J. Geophys. Res., 113, B11403, doi:10.1029/2007JB005280 Ludwig, K.R. and Titterington, D.M. (1994), Calculation of 230Th/U isochrones, ages and errors. Geochimica et Cosmochimica Acta. 58 (22), 5031‐5042. Marco, S., Stein, M., Agnon, A. and Ron, H. (1996), Long‐term earthquake clustering: A 50,000 year paleoseismic record in the Dead Sea Graben. J. Geophys. Res., 101, 6179‐6191. Rotstein, Y., Bruner, I. and Kafri, U., (1993), High‐resolution seismic imaging of the CF and its implications for the structure of Mt. Carmel. Isr. J. Earth Sci., 42, 55‐69. Salamon, A., Hofstetter, A., Garfunkel, Z. and Ron, H. (2003) Seismotectonics of the Sinai subplate‐The eastern Mediterranean region. Geoph. J. Int., 155, 149‐173.
Page 1: Abstracts Volume Archaeoseismology
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Page 9 and 10: the importance of performing absolu
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Page 13 and 14: DISCUSSION Based on detailed field
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Page 31 and 32: Nevertheless the lack of research,
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Page 43 and 44: Table 1: Surface faulting extent re
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Page 57 and 58: RISK ANALYSIS The created hazard ma
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Page 61 and 62: CONCLUSIONS From the palaeostress a
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however, the massive 1995 earthquak
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mapped on the slopes above Qiryat
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1 st INQUA‐IGCP‐567 Internation
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interpreted as either an expression
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The Shepran Cave is located on the
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properties. The mean value of speci
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excavated a deep trench, thus provi
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Fig. 8: Seismic ground shaking may
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elevant qualitative criteria are po
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CONCLUDING REMARKS The exposed exam
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produced by significantly different
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It is possible that a portion of th
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In addition, the Database of histor
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were published by IGME (1983) and E
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The city collapsed and it was aband
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Fig. 4: Slipped lintel in a window
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to overcome shear resistance and in
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Newmark, N.M. (1965). Effects of ea
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associated with various tsunamis (<
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this method, the magnitude of the e
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etween pieces. Fragments have not f
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on the exact date of the earthquake
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THE ARCHAEOLOGICAL ZONE COLOGNE Aft
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affecting the Alcázar was about 50
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archaeoseismology could instead bec
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In the area later occupied by Vilni
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Fig. 2: Assemblage of landforms ass
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Fig. 8: Data and regression for mag
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Fig. 3: Relationships among magnitu
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CONCLUSIONS 1. Spatial distribution
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The stratigraphic sequence (Fig. 4)
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especially in the zones of hanging
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interpretations are based on relati
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Fig. 5: Gray‐scale value laser im
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(~40 cm), F‐ rotated building str
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Index 1 st INQUA‐IGCP‐567 Inter
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