Archaeoseismology and Palaeoseismology in the Alpine ... - Tierra

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Fig. 4: Detailed map of the study location at the intersection of the Pedro Miguel fault with the Camino de Cruces showing the locations and relationships described in the text. 1: Sidehill scarp; 2: Offset terrace riser and Trail; 3: Fault exposure in stream bank; 4: Linear 0.5 m scarp; 5: Scarp; 6: Offset channel wall and fault exposure in bank; 7: Offset stream bank; 8: Landslide: 9: 3 m offset of gulley and fault exposure. CONCLUSIONS Using numerous and independent lines of evidence, we conclude that the Pedro Miguel fault has historically ruptured through this area, producing a right‐lateral surface offset of the Camino de Cruces of about 3 m, consistent with the findings from paleoseismic studies 20 km south. The displacements of all small‐scale geomorphic features are consistent with the amount of displacement of the Camino de Cruces. The observation of Trail cobles under the fault scarp‐derived colluvium strongly supports that the Trail had been completed before the offset. 1 st INQUA‐IGCP‐567 International Workshop on Earthquake Archaeology and Palaeoseismology 34 Fig. 5: Reconstruction of the Trail offset by back‐slipping 2.8 meters along the fault results in a good fit for the pre‐earthquake Trail location. The Trail cobbles and sizes are shown in their surveyed locations. The back‐slipping results in a restoration of the terrace riser, and explains the pattern of pre‐ and post‐ displacement Trail cobbles adjacent to the fault. The only reported earthquake, since the 1530s, large enough to generate a 3‐meter displacement, is the May 2, 1621 Panamá Viejo earthquake. From this we conclude that the last rupture on the Pedro Miguel fault was the AD 1621 event, an earthquake that significantly damaged Panamá Viejo, and if repeated, would strongly shake the modern Panamá City and all of the Panamá Canal structures on the Pacific side. Because the Pedro Miguel fault has long been assumed to be inactive, these findings have been a surprise to the engineering community. Although the exposures of the fault offsetting late Holocene alluvium are geologically convincing, the archeoseismic evidence of the Camino de Cruces being offset by the fault has proven to be invaluable in gaining general acceptance of the seismic hazard posed by the Pedro Miguel fault. Acknowledgments: We thank the Autoridad del Canal de Panamá for their support of this project, especially Luis Alfaro, Pastora Franceschi, Rodrigo Lam, and the Survey Division. We also thank all of the ECI staff that assisted, particularly Danielle Verdugo and Patrick Williams. References ECI (2009). Appendix D: Documenting the Pedro Miguel Fault’s AD 1621 Offset of the Camino de Cruces; in Quantitative Characterization of the Pedro Miguel and Miraflores Faults; unpublished Earth Consultants International consulting report prepared for the Autoridad del Canal de Panamá, February, 2009.
1 st INQUA‐IGCP‐567 International Workshop on Earthquake Archaeology and Palaeoseismology THE BAELO CLAUDIA EARTHQUAKE PROBLEM APPROACHED WITH SEMI‐ QUANTITATIVE LOGIC TREES C. Grützner (1) and K. Reicherter (1) (1) Institute for Neotectonics and Natural Hazards, RWTH Aachen University, Lochnerstr. 4‐20, 52056 Aachen, GERMANY. c.gruetzner@nug.rwth‐aachen.de Abstract: The Roman ruins of Baelo Claudia at the Strait of Gibraltar (Province Cádiz, Southern Spain) show numerous damages on buildings and infrastructure that bear witness of two earthquakes in the 1 st and 4 th Century A.D. Comprehensive fieldwork has been taken out during the last years in order to find the seismic source for the events and to determine earthquake parameters. We briefly categorize the results using the semiquantitative logic tree approaches presented by Atakan et al. (2000) and Sintubin and Stewart (2008). The comparison of the logic trees, which take into account palaeoseismological and archaeoseismological observations, respectively, shows that a complementary application of both analyses can provide a far more reliable evaluation of a study site. Key words: palaeoseismology, archaeoseismology, spain, logic tree ROMAN RUINS OF BAELO CLAUDIA The westernmost part of the Gibraltar arc hosts the Bolonia Bay, close to the city of Tarifa (Fig. 1). Here, the former Roman town of Baelo Claudia dates back to the 2 nd Century BC and was, due to its strategic position, an important trade centre. Main income was earned from tuna‐fishing and garum export (a kind of tuna sauce). The city had approximately 2,000 inhabitants and was surrounded by a massive representative city wall. Main elements of the actual archaeological site are the theatre, the decumanus (main street), the forum area, an eastern and a western gate, the temples area, the basilica, and the macellum (market hall) (Silliéres, 1997; Alonso‐ Villalobos et al., 2003). Almost all parts of the ruins show damages that cannot be explained by ground settling effects, erosion, or vandalism. While some of those features could be identified as related to shallow landslides, many of them are caused by earthquakes (Silva et al., 2006, 2009; Goy et al., 1994). Fig. 1: The Bolonia Bay, location of the Roman remains of the Baelo Claudia village close to the Gibraltar Strait in southern Spain (SRTM data). 35 Among others, those typical damages include penetrative fractures in masonry blocks, pop up‐like deformation of the pavement, corner breakouts of paving stones, dropped keystones of arches, tilted and folded walls, columns that fell in the same directions, and wall offsets. All earthquake damages have been mapped carefully during the last field campaigns and show a clear orientation. Inside the ruins, geophysical prospection methods were used to identify the landslide areas and to map unexcavated remains. Archaeoseismological investigations mainly concentrated on: ‐ Identification of earthquake damages ‐ Classification of earthquake damages ‐ Mapping of cracks and deformation orientations ‐ Geophysical investigation of landslide areas inside the ruins ‐ Dating of event horizons Fig. 2: The Bolonia Bay is surrounded by three steep mounain ranges of Aquitanian calcarenites. Palaeoseismological investigations concentrated on the Sierra de la Plata area. Recent 14 C dating results from the Isis temple and archaeo‐stratigraphic classification indicate two earthquake events in the 1 st and the 3 rd Century AD.
Page 1: Abstracts Volume Archaeoseismology
Page 4 and 5: Edita e imprime: Sección de Public
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Page 9 and 10: the importance of performing absolu
Page 11 and 12: indicative of strike‐slip faultin
Page 13 and 14: DISCUSSION Based on detailed field
Page 15 and 16: Table 1: Source parameters used in
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Page 21 and 22: continuous support. N. Shalev, G. G
Page 23 and 24: The tumulus initial morphology show
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Page 31 and 32: Nevertheless the lack of research,
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Page 35: The site reconnaissance successfull
Page 43 and 44: Table 1: Surface faulting extent re
Page 47 and 48: The graben has a markedly asymmetri
Page 53 and 54: are a valuable addition to the rout
Page 55 and 56: to 400 m) the calculated values for
Page 57 and 58: RISK ANALYSIS The created hazard ma
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Page 61 and 62: CONCLUSIONS From the palaeostress a
Page 63 and 64: Fig. 2: Geological map of the study
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properties. The mean value of speci
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1 st INQUA‐IGCP‐567 Internation
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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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