Archaeoseismology and Palaeoseismology in the Alpine ... - Tierra

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Fig. 4: Differential liquefaction of a stratified bed at a paleoseismic event at 12,400 BP (Mörner, 2003, 2008; site Hunnestad). The material vented behaves quite differently with respect to grain sizes. In a large mushroom structure a laminar flow is recorded by the stratification of sand and course silt grains, a turbulent flow by the totally random distribution of fine grains measured by the anisotropy of magnetic susceptibility (AMS), and a free flow of the very small particles controlling the magnetic polarity (ChRM) allowing a firm orientation with respect to the geomagnetic pole. The spatial distribution of liquefaction as to a single event is more or less linearly related to the magnitude of the earthquake. Liquefaction structures are usually formed at earthquakes of a minimum magnitude in the order of M 5–5.5. This implies that the recording of past liquefactions tells us that the magnitude ought to be, at least, above ~5.5 (with respect to the Richter‐scale). Because earthquakes usually are not single events, but rather a cluster of shocks and after‐shocks, one would expect to see not just one phase of liquefaction, but multiple phases (Mörner, 2003). Fig. 5: Five successive phases (1–5) of liquefaction of the 9663 vBP paleoseismic event, interpreted to represent shocks and after‐shocks of the same earthquake event (from Mörner, 2003, 2008; site: Myra West). Five successive phases were also recorded at a site (Hög) located 35 km away. 1 st INQUA‐IGCP‐567 International Workshop on Earthquake Archaeology and Palaeoseismology) 96 Liquefaction and venting of liquefied material are recorded at numerous sites in Sweden (Mörner, 2003, 2005, 2008). The spatial distribution of one and the same liquefaction event – 320x100 km for the 10,430 vBP event and 80x40 km for the 9663 vBP event – gives evidence of high‐magnitude events. At several events, we were able to record multiple phases of liquefaction. At the 9663 vBP paleoseismic event, we recorded 5 successive phases (Fig. 5), interpreted in terms of shock and after‐shocks. The size and type of liquefaction structures have a bearing on the magnitude. In some cases we have recorded the venting of gravel, even course gravel and pebbles (Figs. 6– 7). This calls for magnitudes in the order of M>8. One such event is dated at 10,388 vBP and another at 6100 BP (Mörner, 2003, 2008). Fig. 6: Venting not only of sand but also gravel and pebbles at the 10,388 vBP event (Mörner, 2003, 2008; site Turinge grusgrop). This calls for a high‐magnitude paleoseismic event (M>8). Fig. 7: Structureless liquefied sand as a part of the venting of sand‐gravel‐pebbles in the Fig. 6 site. Seismic shaking may also generate wavy patterns of previously horizontal sand and clay beds (Fig. 8; cf. Mörner, 2003; Mörner and Sun, 2008). Extensive turbidites are often formed by the sediment masses set in motion by slides, liquefaction and tsunami waves. Their spatial distribution is 300x200 km for the 10,430 vBP event and 320x90 km for the 9663 vBP event. They stick out as distinct “marker‐varves” (Fig. 9). This allows a very precise dating as to the Swedish Varve Chronology.
Fig. 8: Seismic ground shaking may sometimes generate wavy patterns in sand (above) and clay (below) (from Mörner, 2003). The wavy clay layers have increased paleomagnetic intensity suggesting internal fluidization (Mörner and Sun, 2008). Fig. 9: The 9663 vBP turbidite (seismite) of graded bedding, here seen as a distinct marker‐bed witin the annually varved clay (from Mörner, 2003). In Sweden, we have been able to tie the liquefaction events into singular varve years by that providing an annual resolution allowing us to determine spatial and temporal factors. At present, we have identified, dated and described 59 separate paleoseismic events in Sweden (Fig. 10). Most of those generated liquefaction structures (and 16 of them generated tsunami events). All events are recorded by multiple criteria; e.g. primary faults, bedrock fracturing, sediment deformation, liquefaction, slides, tsunami events and turbidites (see the eight papers listed in References). 1 st INQUA‐IGCP‐567 International Workshop on Earthquake Archaeology and Palaeoseismology) 97 Fig. 10: Time distribution in thousands of years BP of the 59 paleoseismic events recorded in Sweden (Mörner, 2003, 2005, 2008, 2009). CONCLUSIONS Liquefaction provides very essential information for the understanding and interpretation of paleoseismic (and archaeoseismic) events. References Mörner, N.‐A., 1996. Liquefaction and varve disturbace as evidence of paleoseismic events and tsunamis: the autumn 10,430 BP event in Sweden. Quat. Sci. Rev., 15, 939‐948. Mörner, N.‐A., 2003. Paleoseismicity of Sweden – a novel paradigm. A contribution to INQUA from its Sub‐commission of Paleoseismology, Reno 2003, ISBN‐91‐631‐4072‐1, 320 pp. Mörner, N.‐A., 2004. Active faults and paleoseismicity in Fennoscandia, especially Sweden: Primary structures and secondary effects. Tectonophysics, 380, 139‐157. Mörner, N.‐A., 2005. An investigation and catalogue of paleoseismology in Sweden. Tectonophysics, 408, 265‐307. Mörner, N.‐A., 2008. Paleoseismicity and Uplift of Sweden. Guidebook, Excursion 11 at 33rd IGC, Oslo 2008, 107 pp, www.33IGC.org. Mörner, N.‐A., 2009. Late Holocene earthquake geology in Sweden. Geol. Soc. London, Spec. Publ., 316, 197‐188. Mörner, N.‐A. & Sun, G., 2008. Paleoearthquake deformations recorded by magnetic variables. Earth Planet Sci. Letters, 267, 495‐502. Mörner, N.‐A., Tröften, P.E., Sjöberg, R., Grant, D., Dawson, S., Bronge, C., Kvamsdal, O. & Sidén, 2000. Deglacial paleoseismicity in Sweden: the 9663 BP Iggesund event. Quat. Sci. Rev., 19, 1461‐1468.
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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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Page 47 and 48: The graben has a markedly asymmetri
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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
Page 59 and 60: 290 m water depth the basin accumul
Page 61 and 62: CONCLUSIONS From the palaeostress a
Page 63 and 64: Fig. 2: Geological map of the study
Page 71 and 72: however, the massive 1995 earthquak
Page 73 and 74: mapped on the slopes above Qiryat
Page 77 and 78: interpreted as either an expression
Page 79 and 80: The Shepran Cave is located on the
Page 87 and 88: properties. The mean value of speci
Page 91 and 92: excavated a deep trench, thus provi
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Page 101 and 102: elevant qualitative criteria are po
Page 103 and 104: CONCLUDING REMARKS The exposed exam
Page 105 and 106: produced by significantly different
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 and 130: this method, the magnitude of the e
Page 133 and 134: etween pieces. Fragments have not f
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Page 139 and 140: THE ARCHAEOLOGICAL ZONE COLOGNE Aft
Page 143 and 144: affecting the Alcázar was about 50
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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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