Archaeoseismology and Palaeoseismology in the Alpine ... - Tierra

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THE ESTIMATION OF SEISMIC PARAMETERS The pertinent data and information including the mechanism of the faults, the appearance and the geometry of the faults and the seismotectonic specifications of the studied area are to be considered in this method. In this regard, the North Tabriz, Bozqoush, Masouleh, Soltaniyeh, Takht‐e‐Solayman, Zanjan and NE1 faults were evaluated. With reference to the magnitude, geometrical specifications and the measured distances of the seismic line sources at the periphery of the site with the aid of reliable attenuation equations, the maximum horizontal and vertical acceleration amounts for the 50% and 84% levels were calculated. Eventually based on the measured parameters calculated by the various attenuation equations with the aid of the logic tree, the NE1 fault was considered as the most important seismic line source at the vicinity of the Moshampa dam and power plant site. Moreover, the acceleration values resulted from its reactivation is recommended to be used as the maximum credible earthquake parameters (MCE) for 50% and 84% levels (Table 1). Table 1: Maximum credible earthquake accelerations Fault Name PGHA(g) PGVA(g) H50% H84% V50% V84% NE1 0.28 0.43 0.19 0.33 The analysis of seismic risk via the probabilistic method comprises of the relationship between the strong earth movement parameters and the possibility of their occurrence at the project site within a specific time period with the aid of mathematical and probabilistic methods. The most important criterion in the aforesaid method is to have access to reliable statistical data of the previous earthquakes in the region. In this study, the point and line seismic sources models were utilized and the tectonic specifications of the site, logic tree method and engineering judgment of maximum horizontal and vertical acceleration parameters at the Moshampa project site for design basic and maximum design earthquakes were recommended (Table 2). Finally, it should be pointed out that due to the tectonic specifications of the Moshampa project site and the conducted studies, the values calculated for the 50% and 84% level are recommended for the final values. Table 2: Seismic design parameters for Moshampa site Earthquake Design Levels Return Period (year) 1 st INQUA‐IGCP‐567 International Workshop on Earthquake Archaeology and Palaeoseismology) Maximum Value of Acceleration (g) 50% 84% V H V H DBE 1000 0.11 0.16 0.19 0.25 MDE 1500 0.14 0.19 0.23 0.29 CONCLUSIONS This article aims at explaining the importance of tectonic and paleseismic studies at the vicinity of vital structures, 128 which shows to have no connection with the seismic point and line sources at the first glance. If only the seismotectonic data of the site’s periphery has been evaluated for the activities of the faults, in other words, the relationship between the faults, historical and the 20 th century epicenters as well as the impact of the faults on the recent sediments have been analyzed, definitely the Takht‐e‐Solayman fault would have been considered as the most important seismic source. Subsequently, the parameters of the earth’s strong movements for the maximum credible earthquake (84% level) for the horizontal and vertical values would have been 0.17g and 0.11g, respectively. These values are much smaller than the results obtained from the point sources, which were calculated for the return period of 10000 years (equivalent to the MCE return period) for the 84% level, horizontal value of 0.45g and vertical value of 0.36g. While the tectonic and paleseismic studies revealed that the NE1 fault segment is the most important seismic scenario at the periphery of Moshampa dam and power plant site. Although no earthquake in relation to the NE1 fault or within the 40‐kilometer radius of the site has been recorded in the 20 th century, this study concludes that the tectonic conditions and the location of the Moshampa dam and power plant site indicates that in the near future (during the normal life time of the structure) the occurrence of a relatively strong earthquake at the periphery of the Moshampa site is highly probable. Acknowledgements: We would like to express our appreciation to Mr. Samani for accompanying in field geology and Mr. Karimi‐Haghighi for editing the paper. References Aghanabati, A. (2006). Geology of Iran. Ministry of Industry and Mine, Geological Survey of Iran, 558 pp. Ambraseys, N. N. and Melville, C. P. (1982). A History of Persian Earthquakes. Cambridge University Press.219pp. Ambraseys, N. N. and Douglas, J. (2003). Near Field Horizontal & Vertical Earthquake Ground Motion. Soil Dynamics and Earthquake Engineering, 23(1), 1‐18. Campbell, K. W. and Bozorgnia, Y. (2003). Updated Near‐Source Ground Motion (Attenuation) Relation for Horizontal and Vertical Components of Peak Ground Acceleration and Acceleration Response Spectra. Bulletin of the Seismological Society of America, 93(1). 314‐331. Jackson, J.A., & McKenzie, D.P. (1984). Active tectonics of the Alpine‐Himalayan belt between western Turkey and Pakistan. Geophys, 77,185‐264. Jackson, J.A., & McKenzie, D.P. (1988). The relationship between plate motions and seismic moment tensors and the rates of active deformation in the Mediterranean and Middle East. Geophys, 93, 45‐73. Samari, H. (2006). Seismotectonics studies on Moshampa dam & HPP site. Tamavan consulting engineers, Tehran‐Iran. ICOLD, (1989). International Commission on Large Dams, “Selecting Seismic Parameters for Large Dams, Guidelines Bulletin 72. Wells, D. L. and Coppersmith, K. J. (1994). “New Empirical Relationships among Magnitude, Rupture Length, Rupture Width, Rupture Area and Surface Displacement”, Bulletin of the Seismological Society of America, 84(4), 974‐1002.
1 st INQUA‐IGCP‐567 International Workshop on Earthquake Archaeology and Palaeoseismology) EVIDENCE FOR A HOLOCENE EARTHQUAKE RECORDED IN A FLUVIAL‐ ARCHAEOLOGICAL SEQUENCE OF THE SEGURA RIVER, SE SPAIN M. Sánchez‐Gómez (1), C. Martínez‐Sánchez (2), F García‐García (1), J.A. Peláez (3), F. Pérez‐Valera (1) and M. Martínez‐Andreu (5) (1) Departamento de Geología, Universidad de Jaén, Campus Las Lagunillas, 23071‐Jaén, SPAIN. msgomez@ujaen.es (2) ArqueoTec, C/ González Adalid 13 2º planta, 30002‐Murcia, SPAIN. consueloms@telefonica.net (3) Departamento de Física, Universidad de Jaén, Campus Las Lagunillas, 23071‐Jaén, SPAIN. japelaez@ujaen.es (4) Museo Arqueológico de Cartagena, C/ Ramón y Cajal 45, 30204‐Cartagena, SPAIN. miguelmarand@yahoo.es Abstract: The archaeological excavation of a rock shelter (Abrigo del Pozo) in one of the slopes of the Segura River (SE Spain) has revealed a exceptionally preserved sedimentary record spanning from the Paleolithic to the present‐day. The sedimentary analysis of the excavation indicates that human occupation was controlled by fluvial environmental evolution. However, an anomalous and continuous layer of large stones results in a disturbance of human occupation and normal fluvial sedimentation. We interpreted the anomalous level as related to a palaeoearthquake responsible for the collapse of the roof and walls of the rock shelter between 5820 +/‐ 50 BP and 3710 +/‐ 40 BP. A nearby earthquake of M 5.5 – 6.0 is the most plausible cause for the collapse. Several regional faults, included the Socovos‐Calasparra fault less than 2 km apart, could be the responsible of the event. Key words: rock shelter, palaeoearthquake. North‐eastern Betics. fluvial sedimentation INTRODUCTION The Betic Cordillera is the Spanish region with highest seismic hazard (Peláez and López‐Casado, 2002). Nevertheless, at present a limited number of studies have issued the effects of palaeoearthquakes (e.g. Silva et al., 1997; Masana et al., 2004). Trench studies constitute an effective tool to establish the seismic history of a fault, but they need to identify previously the fault as least as potentially active. The Betic Cordillera has a composite tectonic history with a large number of mapped faults, most of them being at present inactive. Therefore, one of the main tasks in the region is to recognize large palaeoearthquakes in the geological and archaeological records as well as to identify the associated faults. This work analyzes the sedimentary infilling of a cave, adjacent to the Segura River in SE Spain. This cave has recorded almost continuous human presence since the Palaeolithic and evidence of a catastrophic breakdown. We will propose that this collapse was caused by a seismic event, then examining the implications of this earthquake in the neighbourhood, where no other significant Holocene earthquake is known. This study highlights the potential of archaeological shelters for identifying and dating earthquakes, if they are revisited from a palaeoseismologic point of view. GEOLOGICAL SETTING The Abrigo del Pozo (Pozo Rock Shelter) is located in Sierra del Molino, a carbonate massif belonging to the Prebetic Zone of the Betic Cordillera. The rock shelter is about 30 m‐long, with a maximum depth of 9 m and an average height ≥ 2 m. It is located at the foot of a cliff in a canyon‐shaped valley incised by the Segura River. The present‐day height of the cave floor above the average stream level is about 4 m. The cave section and position in relation to the fluvial channel provide a comfortable and 129 secure habitat. Rock paints and abundant archaeological remnants reveal a reiterated use as prehistoric residence, refuge or sanctuary. Nevertheless, the access is difficult due to its location amid the canyon, this fact having preserved the rock shelter from later alterations and vandalism. Fig. 1: Geological sketch indicating the location of the studied rock shelter. SCF = Socovos‐Calasparra Fault Abrigo del Pozo is only 1,5 km from Socovos‐Calasparra Fault (Fig. 1), a 70 km‐long fault that constitute a major regional structure with geomorphologic evidences of Quaternary displacements (Rodríguez‐Pascua, 1998). During the last century only one mb 4.5 small earthquake (Cieza, June 13 th , 1936) has been located at the eastern end. Nevertheless, other relatively close structures have produced instrumental seismic swarms, including main earthquakes with magnitudes in the range mb 4.0‐5.0
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Abstracts Volume Archaeoseismology
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Edita e imprime: Sección de Public
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1 st INQUA‐IGCP‐567 Internation
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the importance of performing absolu
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indicative of strike‐slip faultin
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DISCUSSION Based on detailed field
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Table 1: Source parameters used in
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elations. However, the attenuation
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mostly concentrated on the DST in I
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continuous support. N. Shalev, G. G
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The tumulus initial morphology show
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our understanding and prediction of
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spans, with a threefold increase fr
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Nevertheless the lack of research,
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earthquake. In uncertain cases, as
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The site reconnaissance successfull
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Table 1: Surface faulting extent re
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The graben has a markedly asymmetri
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are a valuable addition to the rout
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to 400 m) the calculated values for
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RISK ANALYSIS The created hazard ma
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290 m water depth the basin accumul
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CONCLUSIONS From the palaeostress a
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Fig. 2: Geological map of the study
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however, the massive 1995 earthquak
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mapped on the slopes above Qiryat
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interpreted as either an expression
Page 79 and 80: The Shepran Cave is located on the
Page 81 and 82: 1 st INQUA‐IGCP‐567 Internation
Page 87 and 88: properties. The mean value of speci
Page 91 and 92: excavated a deep trench, thus provi
Page 99 and 100: Fig. 8: Seismic ground shaking may
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Page 103 and 104: CONCLUDING REMARKS The exposed exam
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Page 107 and 108: It is possible that a portion of th
Page 109 and 110: In addition, the Database of histor
Page 111 and 112: were published by IGME (1983) and E
Page 115 and 116: The city collapsed and it was aband
Page 119 and 120: Fig. 4: Slipped lintel in a window
Page 121 and 122: to overcome shear resistance and in
Page 123 and 124: Newmark, N.M. (1965). Effects of ea
Page 125 and 126: associated with various tsunamis (<
Page 129: this method, the magnitude of the e
Page 133 and 134: etween pieces. Fragments have not f
Page 137 and 138: on the exact date of the earthquake
Page 139 and 140: THE ARCHAEOLOGICAL ZONE COLOGNE Aft
Page 143 and 144: affecting the Alcázar was about 50
Page 147 and 148: archaeoseismology could instead bec
Page 149 and 150: In the area later occupied by Vilni
Page 155 and 156: Fig. 2: Assemblage of landforms ass
Page 157 and 158: Fig. 8: Data and regression for mag
Page 159 and 160: Fig. 3: Relationships among magnitu
Page 161 and 162: CONCLUSIONS 1. Spatial distribution
Page 163 and 164: The stratigraphic sequence (Fig. 4)
Page 165 and 166: especially in the zones of hanging
Page 169 and 170: interpretations are based on relati
Page 173 and 174: Fig. 5: Gray‐scale value laser im
Page 177 and 178: (~40 cm), F‐ rotated building str
Page 179 and 180: Index 1 st INQUA‐IGCP‐567 Inter
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