Preliminary seismic microzonation of Sivas city (Turkey) using microtremor and refraction microtremor (ReMi) measurements

Sivas city, located in the inner east part of Anatolia (Turkey), is far from seismic sources. However, the city is under risk owing to strong earthquakes occurring around the area, and different soil conditions that can produce variation in the ground motion amplification. Microzonation of cities provides a basis for site-specific hazard analysis in urban settlements. In particular, seismic microzonation can be achieved by means of detailed seismic assessment of the area, including earthquake recordings and geological studies. In this paper, we propose a preliminary microzonation map for the city of Sivas, based on the variation in the dominant periods of the sediments covering the area. The periods are retrieved from microtremor measurements conducted at 114 sites, using the horizontal-to-vertical spectral ratio technique. The results of microtremor analysis were compared with those obtained from refraction microtremor measurements at two profiles crossing the studied area. According to the classification of dominant periods, Sivas area can be divided into four zones, probably prone to different levels of seismic hazard. However, specific studies including analysis of weak earthquakes are required in the future to validate our microzonation map.     

Lösmaterialackumulationer i blockhaven på Varangerhalvön i Nordnorge—en problemdis- kussion

Malmström, B. og Palmér, O.: Lösmaterialackumulationer i blockhaven på Varangerhalvön i Nordnorge—en problemdiskussion. Geografisk Tidsskrift 82: 82–87, Lund, 15. november 1982.

A type of mounds consisting of unconsolidated deposits mainly situated in blockfields is presented. Comparisons are made with pingo-like remnants in northern Scandinavia described by other authors.     

Appraisal of World Reference Base for Soil Resources—from a nordic point of view

During the project “Nordic Reference Soils” 13 different soils from Denmark, Finland, Norway and Sweden were selected in order to represent i) soils covering the main areas of the Nordic area, ii) soils from the different climatic regions, and iii) environmental sensitive soils. The 13 Nordic Reference Soils provided an excellent basis for the evaluation of the WRB (World Reference Base for Soil Resources) performance under Nordic conditions. Classification according to the WRB poses considerable problems. These concern podzolized soils, cultivated soils, and the acid sulfate soils. Only three out of the seven podzolized soils are allocated in taxons reflecting that they were podzolized. Four out of the nine cultivated soils were exposed to substantial anthropogenic impact, resulting in man-made Mollic A-horizons, which is not reflected in the classification. The WRB-classification of the soils is compared with the FAO and Soil Taxonomy classification. This highlighted some of the classification problems. This paper will propose changes to the WRB in order to improve the performance of the system for Nordic soils.

Geografisk Tidsskrift, Danish Journal of Geography 100: 15–26     

Palaeoenvironmental and palaeoecological change on the northern Tethyan carbonate platform during the Late Barremian to earliest Aptian

A major shift from Urgonian oligotrophic carbonate accumulation to orbitolinid‐rich mixed siliciclastic–carbonate deposition is observed near the Barremian–Aptian boundary in many sections both within and outside the shallow‐marine Tethyan Realm. This important facies change in the Swiss Helvetic Alps is documented here and interpreted in the context of general palaeoenvironmental change. To achieve this, a detailed micropalaeontological, sedimentological, mineralogical and geochemical study has been carried out on six sections across the upper part of the lower Schrattenkalk Member (Late Barremian), the Rawil Member (formerly ‘Lower Orbitolina Beds’, earliest Aptian) and the lowermost part of the upper Schrattenkalk Member (Early Aptian). The sediments of the Rawil Member exhibit inner‐platform facies with rudists, miliolids, orbitolinids and dasycladals to outer‐platform facies characterized by small benthic foraminifera, orbitolinids, crinoids and bryozoans. Stratigraphic trends in microfacies environments and the composition of microfossil assemblages, indicate that the Rawil Member includes a transgressive systems tract and the base of a highstand systems tract which are composed of an increasing number of parasequences in distal directions (five to nine in the sections studied here). The sea‐level rise discerned in the Rawil Member is coeval with increased detrital input and phosphorus burial, with maximum values up to 80 times and 21 times the background values in the subjacent part of the lower Schrattenkalk Member, respectively. Furthermore, the Rawil Member records the appearance of kaolinite, indicating a change towards tropical and more humid climate conditions. This change may have led to an increase in continental weathering rates and an associated increase in detrital and nutrient fluxes towards the ocean. The phase of climate change observed near the Barremian–Aptian boundary may have been triggered by a phase of intensified volcanic activity linked with the onset of the Ontong Java large igneous province and the Rawil Member may be the expression of a precursor episode to Oceanic Anoxic Event 1a in the shallow‐marine environment.     

A new radiocarbon chronology of Baumkirchen,stratotype for the onset of the Upper Würmian in the Alps

The start of the Upper Würmian in the Alps was marked by massive fluvioglacial aggradation prior to the arrival of the Central Alpine glaciers. In 1984, the Subcommission on European Quaternary Stratigraphy defined the clay pit of Baumkirchen (in the foreland of the Inn Valley, Austria) as the stratotype for the Middle to Upper Würmian boundary in the Alps. Key for the selection of this site was its radiocarbon chronology, which still ranks among the most important datasets of this time interval in the Alps. In this study we re‐sampled all available original plant specimens and established an accelerator mass spectrometry chronology which supersedes the published 40‐year‐old chronology. The new data show a much smaller scatter and yielded slightly older conventional radiocarbon dates clustering at ca. 31 ¹⁴C ka BP. When calibrated using INTCAL13 the new data suggest that the sampled interval of 653–681 m in the clay pit was deposited 34–36 cal ka BP. Using two new radiocarbon dates of bone fragments found in the fluvioglacial gravel above the banded clays allows us to constrain the timing of the marked change from lacustrine to fluvioglacial sedimentation to ca. 32–33 cal ka BP, which suggests a possible link to the Heinrich 3 event in the North Atlantic. Copyright © 2013 John Wiley & Sons, Ltd.     

Lime Stabilization of Soils Underlying a Salt Evaporation Pond: A Laboratory Study

The purpose of this article is to investigate a possible use of lime for the stabilization of base soils underlying salt evaporation ponds in Çamalt? Solar Marine Salt Plant. The plant is located on the old Gediz River Delta, on the north shore of the Izmir Bay-Turkey, where alluvial deltaic soft marine sediments constitute the local soil condition. The low bearing capacity of the pond base soils results in some problems on the mechanical harvest of the solar salt. Therefore, stabilization was taken into consideration for improving the productivity of the salt plant. For this purpose, bench-scale laboratory tests were performed on the specimens that had been sampled from the bases of the salt evaporation pond to investigate the influence of lime on the unconfined compressive strength (UCS) of these marine sediments. By interpreting the pH test results and consistency limits of the lime stabilized soils, optimum lime content was determined as 8%. The verification of the long-term pozzolanic reactions for the optimum lime content was conducted by performing UCS tests with up to six months curing periods, along with the microstructural analysis through X-ray diffraction analysis (XRD) and a scanning electron microscope (SEM). Long-term tests revealed that the optimum lime content successfully sustained the required pozzolanic reactions, and a strength gain of 500% was achieved for a six-month curing period.     

A high-resolution aftershock seismicity image of the 2002 Sultandaği-Çay earthquake (Mw = 6.2), Turkey

A moderate-size earthquake (Mw = 6.2) occurred on 3 February 2002 (07:11:28 GMT) in the Sultanda??-Çay region of southwest Turkey. The mainshock was followed by a strong aftershock of Mw = 6.0 just 2 h after the mainshock, at 09:26:49 GMT. A temporary seismic network of 27 vertical component seismometers was installed to monitor aftershock activity. One thousand sixty nine aftershocks (0.2 < ML < 3.3) were recorded during the period from 5 to 10 February 2002. We analyzed the P and S arrival times and P wave first motion data to obtain high-quality hypocenters and focal mechanisms, which revealed fine details of the fault zone. We infer that the mainshock has ruptured a segment of the Sultanda? Fault Zone that is approximately 37 km long and 7 km wide at depth. The average slip over the rupture plane during the mainshock is estimated to be 32 cm. The linear distribution of the aftershocks and the location of the mainshock epicenter suggest that rupture has initiated in the eastern bending of the fault and propagated unilaterally to the west. The majority of fault plane solutions indicate E–W to ESE–WNW striking oblique–normal faulting mechanisms with an average dip angle of 62° N ± 10° . The high-resolution aftershock seismicity image also shows that faulting involved a complex array of synthetic and possibly antithetic structures during the evolution of the aftershock sequence. The steady increase of the b value towards the west implies that the highest moment release of the mainshock occurred to the west of the epicenter. The study clearly shows the activation of the WNW–ESE-trending Sultanda? Fault Zone along the southern margin of the Ak?ehir-Afyon Graben (AAG). The westernmost end of the aftershock activity corresponds to a structurally complex zone distinct from the main rupture. It is characterized by both ENE–WSW- and NNE–SSW-trending oblique-slip normal faulting mechanisms, the latter being associated with the NNE–SSW-trending Karam?k Graben. The intersection of these two grabens, AAG and Karam?k Graben, provides abundant faults available for failure in this region. The occurrence pattern of large events in recent years indicates a possible migration of earthquakes from east to west. Thus, we conclude that this has an important implication for earthquake hazard for the city of Afyon, which lies along the same fault line and only 20 km west of the termination point of the aftershock zone.     

Geotechnical evaluation of slope and ground failures during the 8 October 2005 Muzaffarabad earthquake, Pakistan

A large devastating earthquake with a magnitude of 7.6 struck in Kashmir on Oct. 8, 2005. The largest city influenced by the earthquake was Muzaffarabad. Balakot town was the nearest settlement to the epicenter, and it was the most heavily damaged. The earthquake caused extensive damage to housing and structures founded on loose deposits or weathered/sheared rock masses. Furthermore, extensive slope failures occurred along Neelum and Jhelum valleys, which obstructed both river flow and roadways. In this article, failures of natural and cut slopes as well as other ground failures induced by the earthquake and their geotechnical evaluation are presented, and their implications on civil infrastructures and site selection for reconstruction and rehabilitation are discussed. It is suggested that if housing and constructions on soil slopes containing boulders as observed in Balakot and Muzaffarabad are allowed, there should be a safety zone between the slope crest and allowable construction boundary.