Geomorphological Criteria Research Articles

Preface "Landslide hazard and risk assessment at different scales"

Department of Geography and Regional Research, Vienna, AustriaCorrespondence to: P. Reichenbach (paola.reichenbach@irpi.cnr.it)The special issue of Natural Hazards and Earth SystemSciences entitled “Landslide hazard and risk assessment atdifferent scales” contains 6 of more than 20 oral and postercontributions originally presented in the session NH3.9 –“Landslide risk assessment methods and strategies” held atthe General Assembly of the European Geosciences Union,in Vienna, Austria, on 7 May 2010. Topics discussed in thesession included the following: (i) heuristic, statistical, deter-ministic, and physically based methods and models to eval-uate landslide susceptibility and hazard, and (ii) evaluationof qualitative and quantitative vulnerability and risk assess-ments based on different data. During the session, variouscontributions were discussed dealing with landslide hazardand risk assessment at local, regional or national scales, indifferent physiographic, climatic and geological settings.The meeting proved a valuable opportunity to discuss andcompare methods, techniques, and tools for the identifica-tion, evaluation, and mitigation of landslide hazards and theassociated risks. Despite the large number of contributionspresenting case study applications to evaluate landslide haz-ards and risk, information on the quality, the reliability andthe limitations of the applied models was not analyzed indetail and should be considered a major issue for future re-search. In the following, we summarize the content and themain results of the papers originally presented and discussedat the meeting that are published in this special issue.Floris et al. (2011) exploit spatial data available in Ital-ian WebGIS portals to evaluate landslide susceptibility ofthe Euganean Hills Regional Park, located SW of Padua, NEItaly. In the paper, quality, applicability and possible analysisscales of the online data were investigated and a susceptibil-ity analysis of the study area was completed using a prob-abilistic approach that compared landslide distribution andthe influencing factors. The input factors used in the analysisinclude landslide distribution, morphometric data (i.e., ele-vation, slope, curvature, profile and plan curvature) and non-morphometric data (i.e., land use, distance to roads and dis-tance to rivers). Attention was paid to data pre-processing, inparticular to the re-classification of continuous data that wasperformed following objective, geologic, and geomorpholog-ical criteria. The results show that the simple probabilisticapproach used for the susceptibility evaluation was accurateand precise (repeatability). Heuristic, statistical, or determin-istic methods could be applied to the online data to improvethe prediction. The data available online for Italy allow forthe assessment of landslide susceptibility at medium to smallscales. Morphometric factors, including terrain elevation andslope angle, provide significant information where lithologi-cal and structural data are not available. The main drawbackof the online data sources was the lack of information on thetemporal frequency of landslides. For this reason, a completehazard analysis is not possible.Pereira et al. (2012) use a bivariate statistical model toidentify a combination of landslide predisposing factors thatbest predicted landslide susceptibility in the Santa Marta dePenagui˜ao study area (70km

The combination of DInSAR and facility damage data for the updating of slow-moving landslide inventory maps at medium scale

Abstract. Testing innovative procedures and techniques to update landslide inventory maps is a timely topic widely discussed in the scientific literature. In this regard remote sensing techniques – such as the Synthetic Aperture Radar Differential Interferometry (DInSAR) – can provide a valuable contribution to studies concerning slow-moving landslides in different geological contexts all over the world. In this paper, DInSAR data are firstly analysed via an innovative approach aimed at enhancing both the exploitation and the interpretation of remote sensing information; then, they are complemented with the results of an accurate analysis of survey-recorded damage to facilities due to slow-moving landslides. In particular, after being separately analysed to provide independent landslide movement indicators, the two datasets are combined in a DInSAR-Damage matrix which can be used to update the state of activity of slow-moving landslides. Moreover, together with the information provided by geomorphological maps, the two datasets are proven to be useful in detecting unmapped phenomena. The potentialities of the adopted procedure are tested in an area of southern Italy where slow-moving landslides are widespread and accurately mapped by using geomorphological criteria.

Interaction between continental and estuarine waters in the wetlands of the northern coastal plain of Samborombón Bay, Argentina

On the Samborombón Bay coastline, located in the Río de la Plata estuary in Buenos Aires province (Argentina), a complex hydrological system has developed at the interface between continental and estuarine water, where significant wetlands develop. The main hydrogeological units, namely the shell ridges, the tidal plain and the marsh areas, have been identified using geomorphological criteria. Water table, hydrochemical and isotopic data have been used to determine their hydrological features, as well as those of the streams and canals. Evaporation processes, in particular, have been considered when depicting chemical and isotopic changes in surface waters in streams and marsh areas. The shell ridges represent a hydrogeological unit in which rainwater is stored, constituting a lens-shaped freshwater aquifer. In this unit, just as in the tidal plain, carbonate dissolution and ion exchange are the main processes regulating water chemistry. On the other hand, in the marsh and surface waters, processes such as mixing with estuarine water and evaporation predominate. These processes control water fluxes and the salinity of the wetland areas and, consequently, their ability to preserve the existing biodiversity. This study shows the importance of knowledge of hydrochemical processes in any proposal concerning the management and preservation of this type of wetland.

Risk Assessment of Beach–Dune System Erosion: Beach Management Impacts on the Balearic Islands

Roig-Munar, F.X.; Martin-Prieto, J.A.; Rodriguez-Perea, A.; Pons, G.X.; Gelabert, B., and Mir-Gual, M., 2012. Risk assessment of beach-dune system erosion: beach management impacts on the Balearic Islands. Journal of Coastal Research, 28(6), 1488-1499. Coconut Creek (Florida), ISSN 0749-0208. The beach-dune system is a sedimentary environment that is fragile and dynamic. Any change to it can have potential adverse effects on its stability. In recent decades, this environment has been heavily exploited for recreation with management practices that do not have enough consideration of protective and aesthetic values. As a result, erosion has increased—mainly in the foredunes—and upset the balance of the beach-dune system. The assessment of the morphoecological conservation state plays a major role in forecasting natural hazard impacts. This paper correlates the most frequented sectors with the most eroded parts in four beach-dune systems of the Balearic Islands (two in Majorca and two in Minorca) through the Digital Shoreline Analysis System. The four beaches show that the coastline retreats at locations with the highest attendance. Two situations may arise as a function of the management practices employed: (1) the beach and foredune area is eroded or (2) the beach-dune system recovers. The paper also describes appropriate beach and foredune management practices that allow recovery of a system degraded by human activity. We compare these practices with strategies adopted at beaches solely for commercial gain in the Balearic Islands. A space-time evolution, from 1956 to 2008, of 78 beaches of the Balearic Islands was carried out through multivariate analysis of a checklist of beach-dune features and management measures. The results show that beach-dune management based on geomorphological criteria improves conservation of the natural system and minimises risk of erosion. Recovery of vegetation is also encouraged.

Geoarchaeological reconstruction of the Caverna de las Brujas (Mendoza, Argentina) for the planning of an archaeological intervention

Archaeological prospection and excavation in the Caverna de las Brujas (southern part of the province of Mendoza, Argentina) has offered the first known data on human presence in this cave. This is of great interest for understanding the evolution of peopling in the southern Mendoza province during the Holocene. Four archaeological pits were excavated, two in the gallery known as the Sala de la Virgen and another two near the cave entrance. Three volcanic ash levels were dated by TL techniques (7780 ± 600, 4700 ± 500; 765 ± 200 years) and a level with enough organic material was dated by 14C analysis (3695 ± 65 years BP). The available data is sufficient to establish the origin and make a geomorphological reconstruction of the Holocene levels. At the same time, a hypothetical model is proposed that uses geomorphological criteria to predict the stratigraphy of the unexcavated lower levels at the cave entrance. The aim of this model is to help direct future archaeological excavations of the cave's oldest deposits.

Using online databases for landslide susceptibility assessment: an example from the Veneto Region (northeastern Italy)

Abstract. In this paper, spatial data available in the Italian portals was used to evaluate the landslide susceptibility of the Euganean Hills Regional Park, located SW of Padua (northeastern Italy). Quality, applicability and possible analysis scales of the online data were investigated. After a brief overview on the WebGIS portals around the world, their contents and tools for natural risk analyses, a susceptibility analysis of the study area was carried out using a simple probabilistic approach that compared landslide distribution and influencing factors. The input factors used in the analysis depended on available data and included landslides, morphometric data (elevation, slope, curvature, profile and plan Curvature) and non-morphometric data (land use, distance to roads and distance to rivers). Great attention was paid to the pre-processing step, in particular the re-classification of continuous data that was performed following objective, geologic and geomorphologic criteria. The results of the study show that the simple probabilistic approach used for the susceptibility evaluation showed quite good accuracy and precision (repeatability). However, heuristic, statistical or deterministic methods could be applied to the online data to improve the prediction. The data available online for the Italian territory allows susceptibility assessment at medium and large scales. Morphometric factors, such as elevation and slope angle, are important because they implicitly include information that is not available, such as lithologic and structural data. The main drawback of the Italian online databases is the lack of information on the frequency of landslides; thus, a complete hazard analysis is not possible. Despite the good results achieved to date, collection and sharing of data on natural risks must be improved in Italy and around the world. The creation of spatial data infrastructure and more WebGIS portals is desirable.

An application of regional time and magnitude predictable model for long-term earthquake prediction in the vicinity of October 8, 2005 Kashmir Himalaya earthquake

A regional time and magnitude predictable model has been applied to estimate the recurrence intervals for large earthquakes in the vicinity of 8 October 2005 Kashmir Himalaya earthquake (25°–40°N and 65°–85°E), which includes India, Pakistan, Afghanistan, Hindukush, Pamirs, Mangolia and Tien-Shan. This region has been divided into 17 seismogenic sources on the basis of certain seismotectonics and geomorphological criteria. A complete earthquake catalogue (historical and instrumental) of magnitude Ms ≥ 5.5 during the period 1853–2005 has been used in the analysis. According to this model, the magnitude of preceding earthquake governs the time of occurrence and magnitude of future mainshock in the sequence. The interevent time between successive mainshocks with magnitude equal to or greater than a minimum magnitude threshold were considered and used for long-term earthquake prediction in each of seismogenic sources. The interevent times and magnitudes of mainshocks have been used to determine the following predictive relations: logTt = 0.05 Mmin + 0.09 Mp − 0.01 log M0 + 01.14; and Mf = 0.21 Mmin − 0.01 Mp + 0.03 log M0 + 7.21 where, Tt is the interevent time of successive mainshocks, Mmin is minimum magnitude threshold considered, Mp is magnitude of preceding mainshock, Mf is magnitude of following mainshock and M0 is the seismic moment released per year in each seismogenic source. It was found that the magnitude of following mainshock (Mf) does not depend on the interevent time (Tt), which indicates the ability to predict the time of occurrence of future mainshock. A negative correlation between magnitude of following mainshock (Mf) and preceding mainshock (Mp) indicates that the larger earthquake is followed by smaller one and vice versa. The above equations have been used for the seismic hazard assessment in the considered region. Based on the model applicability in the studied region and taking into account the occurrence time and magnitude of last mainshock in each seismogenic source, the time-dependent conditional probabilities (PC) for the occurrence of next shallow large mainshocks (Ms ≥ 6.5), during next 20 years as well as the expected magnitudes have been estimated.

Seamount Characteristics and Mine-Site Model Applied to Exploration- and Mining-Lease-Block Selection for Cobalt-Rich Ferromanganese Crusts

Regulations are being developed through the International Seabed Authority (ISBA) for the exploration and mining of cobalt-rich ferromanganese crusts. This paper lays out geologic and geomorphologic criteria that can be used to determine the size and number of exploration and mine-site blocks that will be the focus of much discussion within the ISBA Council deliberations. The surface areas of 155 volcanic edifices in the central equatorial Pacific were measured and used to develop a mine-site model. The mine-site model considers areas above 2,500 m water depth as permissive, and narrows the general area available for exploration and mining to 20% of that permissive area. It is calculated that about eighteen 100 km2 exploration blocks, each composed of five 20 km2 contiguous sub-blocks, would be adequate to identify a 260 km2 20-year-mine site; the mine site would be composed of thirteen of the 20 km2 sub-blocks. In this hypothetical example, the 260 km2 mine site would be spread over four volcanic edifices and comprise 3.7% of the permissive area of the four edifices and 0.01% of the total area of those four edifices. The eighteen 100 km2 exploration blocks would be selected from a limited geographic area. That confinement area is defined as having a long dimension of not more than 1,000 km and an area of not more than 300,000 km2.

Identification and characteristics of surge-type glaciers on Novaya Zemlya, Russian Arctic

AbstractWe present a comprehensive new inventory of surge-type glaciers on the Novaya Zemlya archipelago, using high-resolution (up to 4 m) satellite imagery from 1976/77 (Hexagon), 1989 (Landsat TM), 2001 (Landsat ETM+) and 2006 (ASTER). A total of 692 glaciers and their forelands were observed for glaciological and geomorphological criteria indicative of glacier surging (e.g. looped moraines, heavy surface crevassing, surface potholes, thrust-block moraines, concertina eskers). This enabled the identification of 32 potential surge-type glaciers (compared with four previously identified) representing 4.6% of the total but 18% by glacier area. We assess the characteristics of surge-type glaciers. Surge-type glaciers are statistically different from non-surge-type glaciers in terms of their area, length, surface slope, minimum elevation, mid-range elevation and terminus type. They are typically long (median length 18.5 km), large (median area 106.8 km2) outlet glaciers, with relatively low overall surface slopes (median slope 1.7°) and tend to terminate in water (marine or lacustrine). They are predominantly directed towards and located in the more maritime western region of the Russian Arctic, and we suggest that surge occurrence might be related to large and complex catchment areas that receive increased delivery of precipitation from the Barents Sea.

Constraint Mapping as a Means of Further Refining Saltmarsh Re-Creation Opportunities for the UK Solent Region

Based on geomorphological criteria, the Coastal Habitat Management Plan (CHaMP) for the Solent identified some 4,800 hectares of land potentially suitable for the creation of intertidal habitat, principally saltmarsh, through the use of managed realignment. Using “constraint mapping,” this study set out to illustrate that limitations to habitat re-creation through inundation are not merely geomorphological in nature. Indeed, a broad range of social, political, legal, technical, and economic constraints exist and must be evaluated in conjunction with physical parameters if the objectives of the European Birds and Habitats Directives are to be met, and so that future coastal defense policies ensure maintenance of the “favorable conservation status” of designated sites. A numerical filter system has been used to re-evaluate individual sites to establish “realistic” opportunities for compensatory saltmarsh creation in the Solent. As a result of taking into account wider socioeconomic constraints, it is clear that fewer areas are available for habitat creation purposes than were initially identified in the Solent CHaMP study.

First-level liquefaction hazard mapping of Laoag City, Northern Philippines

During the 1990 Luzon earthquake (Ms 7.8), the central part of Luzon Island, Philippines suffered much from liquefaction-related processes. Examination of inventories shows that the affected areas lie on certain geological environments that are characteristically vulnerable to liquefaction. Based on this local experience and the findings of earlier workers correlating geological setting with liquefaction susceptibility, a first-level map of liquefaction hazard for Laoag City, Northern Philippines, was produced. Distinct micro-geomorphological units were identified within the mainly fluvio-deltaic setting of the study area. The liquefaction susceptibility of each unit was then ranked as high, moderate, low or non-liquefiable, taking also the geomorphological evolution of the area into account. The geomorphological model of the fluvio-deltaic basin was tested against the results of the georesistivity survey carried out in this study. Moreover, compatibility of the liquefaction susceptibility map with historical liquefaction records supported the validity of the proposed ranking. The study showed that microzonation based on geomorphological criteria is indeed very useful in less-developed countries like the Philippines, where funds for a more rigorous determination of liquefaction potential are limited and not always available.

Mise en évidence d’une dynamique de fleuves de glace durant la glaciation ordovicienne par l’enregistrement géomorphologique

On Contemporary Ice streams the most important factor controlling polar ice-sheet sheet stability and ice flowing occurs in ice streams. On Pleistocene Ice Sheet, Ice stream can be located using several geomorphologic criteria predict from known characteristic of contemporary ice streams, these criteria defining the conceptual Ice Stream land system model. But nowadays, during fossil glaciations, ice streams characterization is still poorly documented and only few studies illustrate fast ice velocity. In this work, we characterize geomorphological markers of ice stream activity in order to define the Ordovician ice stream glacial landsystem. The study area is located in Sahara from Niger to Algeria. In this area, Ordovician glacial landforms have been investigated using satellite images and field investigations. According to these observations, Ordovician paleo ice stream are characterize by their size (20 to 200 km), by the increase of the length or ratio L/l of sub-glacial lineations changing from ice flute to mega scale glacial lineation at the margin of the ice sheet, by the evolution of sub glacial valley morphology ranging from areal scouring to glacial linear incision, and by sub glacial deformation. Finally, marine outlet of ice stream show ice contact deltas deposit. Individually, these criteria may not necessarily be exclusive to ice stream activity, but collectively they are thought to discriminate the characteristic Ordovician ice stream landsystem.

Formalising an inversion methodology for reconstructing ice‐sheet retreat patterns from meltwater channels: application to the British Ice Sheet

AbstractGlacial meltwater channels yield important information regarding patterns of palaeo‐ice‐sheet retreat. However, it is important to distinguish between channels formed at different positions in relation to the ice mass (e.g. lateral, subglacial). In Britain, whilst meltwater channels have been widely reported in the literature, such categorisation is often lacking. Here we develop an inversion methodology for extracting ice margin retreat patterns from meltwater channels. Diagnostic geomorphological criteria are presented, derived from published descriptions of meltwater channel form, by which a channel of unknown origin may be assigned to its appropriate category. These criteria are applied to channels recorded in the BRITICE GIS database of glacial landforms and we find most channels to be of lateral or subglacial origin. The categorisation of channels enables palaeomargin positions and the direction of retreat‐stage ice flow to be approximated, and a preliminary reconstruction is made of fragments of the ice‐sheet retreat pattern. Further mapping and integration of melt traces with other geomorphic data will permit a more complete palaeo‐glaciological reconstruction of the last British Ice Sheet. Copyright © 2007 John Wiley & Sons, Ltd.

A Pragmatic Approach to Seismic Parameters in a region with Low Seismicity: The Case of Eastern Iberia

In intra-plate regions with low-seismic activity, seismic cycles last between 103 and 105 years and, consequently, quiescent faults may be capable of producing catastrophic earthquakes. Paleoseismic studies, which are necessary to define capable faults in these regions and to establish their seismic parameters, are scarce and not always possible. In order to overcome the scarcity of paleoseismic data, this paper proposes an approach to evaluate the capability and seismic parameters of faults. This approach takes into account instrumental, historical, paleoseismological and geological data. Assuming that in a given structural region with definite climatic and geological characteristics similar geomorphic features reflect a similar structural-seismic evolution, the capability of faults is established by comparing the fault related geomorphic features of the few proven seismogenic faults with those of the rest of the faults. The seismic parameters were estimated using some mathematical relationships from geological and geomorphological data, where the slip rate of the faults was determined from geological and geomorphological criteria. The case of eastern Iberia is presented to illustrate this approach. This area is characterized by low seismicity, few historical destructive earthquakes, and only one fault with good paleoseismological data. Of the 249 potential faults (longer than 10 km and adequately oriented with respect to the current stress field), 23 were regarded as capable faults. Some of these were located in seismic quiescent areas, and their main seismic parameters were estimated.

THE RISE OF THE SUN: LEGAL ARGUMENTS IN OUTER CONTINENTAL MARGIN DELIMITATIONS

This article is a prospective analysis of whether the established principles for delimitation of the continental shelf within 200 NM will apply for delimitation of outer continental margins. On the basis of the established normative jurisprudence of delimitations within 200 NM it can namely not be ruled out that the established equitable criteria and methods for delimitation, for finding an equitable solution, were solely set to prevail in delimitations within 200 NM.Title commands delimitation and the title for the zone beyond 200 NM differ from the title within 200 NM. Wherein the distance criterion is the title for the zone within 200 NM, geological and geomorphologic criteria are the basis of the title for the legal continental shelf that extends 200 NM. Accordingly, the established normative principles in delimitation of continental shelves beyond 200 NM are susceptible to differ from the established prevailing principles within 200 NM and may have an important impact on delimitations in the continental outer margins.In conclusion it is held that the established equitable criteria and methods in order to find an equitable solution in delimitations within 200 NM are likely not to apply mutatis mutandis for delimitations beyond 200 NM

Geotechnical Site Characterisation in the Umbria-Marche Area and Evaluation of Earthquake Site-Response

In this research a site classification is proposed for the Umbria-Marche area (central Italy), based on geotechnical and geomorphological criteria. Two empirical techniques to evaluate site effects are used, namely the generalised spectral inversion, and the horizontal to vertical spectral ratio. The soil transfer functions obtained by the two techniques are compared in order to capture the features common to each class and verify the accuracy of the classification. We used strong ground motions recorded during the Umbria-Marche seismic sequence (September 1997-May 1998) and we selected 25 sites that were classified into four groups. The results of the empirical techniques have also been tested using theoretical 1-D or 2-D methods that are commonly used to simulate linear soil behaviour. The results, expressed in terms of amplitude transfer functions, are shown according to each soil class and confirm the consistency of the site characterisation. The empirical techniques are efficient in detecting the fundamental frequency of vibration but seldom the higher harmonics. Conversely, the peak amplitude of the transfer functions is not consistently determined, especially for sites located in deep sedimentary basins, where 2-D effects occur and simplified methods, such as the horizontal to vertical spectral ratios (HVSR) or 1-D theoretical models frequently fail. Significant amplifications are also found for 2-D rock structures such as rock crests or cliffs.

A geohazard reconnaissance study based on geoscientific information for development needs of the western region of Istanbul (Turkey)

The role of geoenvironmental information is becoming increasingly important as legislative changes have forced developers and planning authorities to consider more implications and impact on the environment of large-scale development initiatives. Therefore, integration of surface and subsurface geoscientific information for development needs has prime importance and provides a means of identifying potential problems and opportunities at an early stage in any planned development. However, from the experience of recent natural disasters, it is evident that this was not case the taken into consideration in many countries. In addition to thousands of casualties, many urbanized areas, industrial districts and large-scale engineering structures suffered severe damages from the natural hazards due to many reasons including the lack of preliminary engineering geological maps and zoning maps of the settlement areas. Turkey is one of the countries which is exposed to natural hazards such as earthquakes, landslides and floods. In particular, the devastating 1999 Kocaeli earthquake, which affected the Marmara Region of Turkey, focused the attention on densely urbanized and industrialized metropolitan areas such as Istanbul. The rapid growth of Istanbul, particularly towards west with minimal geoscientific information resulted in an overwhelming pressure on the natural environment. In addition, a large earthquake, which is expected to occur in the Marmara Sea within the next 30 years, also pose a threat to the city and its surroundings. In this study, on the basis of the geological, geomorphological and geophysical reconnaissance study, an integrated geoscientific data were collected from the western region of Istanbul and evaluated for geohazards. The paper focuses on the geological and geomorphological aspects that control the occurrence of some geohazards such as earthquake-induced liquefaction, landslides and flooding. In this context, the geological map of the region was revised and Quaternary deposits were classified into 11 units, in detail. Liquefaction-prone areas were evaluated by using geomorphological criteria based on field investigation, by the examination of the available records from 88 boreholes drilled on recent deposits and by the data from resistivity profiles. The landslides within the region were classified according to their type, relative depth and activity. In addition, fluvial and marine flood-prone areas were also delimited within the region. Finally, a series of maps such as landslide inventory maps, and maps showing liquefaction- and flood-prone areas were produced with the aid of Geographic Information Systems (GIS) to assist in designing further detailed site investigations and to reduce costs by ensuring a more focused approach to strategic planning and site selection.

Basal processes beneath an Arctic glacier and their geomorphic imprint after a surge, Elisebreen, Svalbard

The foreground of Elisebreen, a retreating valley glacier in West Svalbard, exhibits a well-preserved assemblage of subglacial landforms including ice-flow parallel ridges (flutings), ice-flow oblique ridges (crevasse-fill features), and meandering ridges (infill of basal meltwater conduits). Other landforms are thrust-block moraine, hummocky terrain, and drumlinoid hills. We argue in agreement with geomorphological models that this landform assemblage was generated by ice-flow instability, possibly a surge, which took place in the past when the ice was thicker and the bed warmer. The surge likely occurred due to elevated pore-water pressure in a thin layer of thawed and water-saturated till that separated glacier ice from a frozen substratum. Termination may have been caused by a combination of water drainage and loss of lubricating sediment. Sedimentological investigations indicate that key landforms may be formed by weak till oozing into basal cavities and crevasses, opening in response to accelerated ice flow, and into water conduits abandoned during rearrangement of the basal water system. Today, Elisebreen may no longer have surge potential due to its diminished size. The ability to identify ice-flow instability from geomorphological criteria is important in deglaciated terrain as well as in regions where ice dynamics are adapting to climate change.

An application of the time- and magnitude-predictable model to long-term earthquake prediction in eastern Anatolia

In order to estimate the recurrence intervals for large earthquakes occurring in eastern Anatolia, this region enclosed within the coordinates of 36∘–42∘N, 35∘–45∘E has been separated into nine seismogenic sources on the basis of certain seismological and geomorphological criteria, and a regional time- and magnitude-predictable model has been applied for these sources. This model implies that the magnitude of the preceding main shock which is the largest earthquake during a seismic excitation in a seismogenic source governs the time of occurrence and the magnitude of the expected main shock in this source. The data belonging to both the instrumental period (MS≥ 5.5) until 2003 and the historical period (I0≥ 9.0 corresponding to MS≥ 7.0) before 1900 have been used in the analysis. The interevent time between successive main shocks with magnitude equal to or larger than a certain minimum magnitude threshold were considered in each of the nine source regions within the study area. These interevent times as well as the magnitudes of the main shocks have been used to determine the following relations: $$\log T_t= 0.11M_{\min} - 0.12M_p - 0.11\log M_0 + 2.51$$ $$M_f= 0.89M_{\min} - 0.24M_p + 0.31\log M_0 - 4.99$$ fwawhere Tt is the interevent time measured in years, Mmin is the surface wave magnitude of the smallest main shock considered, Mp is the magnitude of the preceding main shock, Mf is magnitude of the following main shock, and M0 is the released seismic moment per year in each source. Multiple correlation coefficient and standard deviation have been computed as 0.50 and 0.28, respectively for the first relation. The corresponding values for the second relation are 0.64 and 0.32, respectively. It was found that the magnitude of the following main shock Mf does not depend on the preceding interevent time Tt. This case is an interesting property for earthquake prediction since it provides the ability to predict the time of occurrence of the next strong earthquake. On the other hand, a strong negative dependence of Mf on Mp was found. This result indicates that a large main shock is followed by a smaller magnitude one and vice versa. On the basis of the first one of the relations above and taking into account the occurrence time and magnitude of the last main shock, the probabilities of occurrence P(Δ t) of main shocks in each seismogenic source of the east Anatolia during the next 10, 20, 30, 40 and 50 years for earthquakes with magnitudes equal 6.0 and 7.0 were determined. The second of these relations has been used to estimate the magnitude of the expected main shock. According to the time- and magnitude-predictable model, it is expected that a strong and a large earthquake can occur in seismogenic Source 2 (Erzincan) with the highest probabilities of P10 = 66% (Mf = 6.9 and Tt = 12 years) and P10 = 44% (Mf = 7.3 and Tt = 24 years) during the future decade, respectively.

Liquefaction potential and susceptibility mapping in the city of Yalova, Turkey

This study presents results of both field and laboratory tests that have been used to asses liquefaction susceptibilities of the soils in Yalova city, located in the well-known seismically active North Anatolian Fault Zone. Liquefaction potentials of the sub-surface materials in Yalova city were estimated by using the standard penetration test (SPT) method of field testing. The data obtained have been mapped according to susceptibility, and the susceptibility maps based on the geotechnical data indicated a moderate to high susceptibility to liquefaction for the magnitude of earthquake of M=7.4. Both the high groundwater level and the grain size of the soils, in conjunction with the active seismic features of the region, result in conditions favourable to the occurrence of liquefaction. When the surface and near surface geological conditions were taken under consideration, it was seen that the study area’s geology is prone to liquefaction having a moderate liquefaction susceptibility. If geologic and geomorphological criteria are considered, it should be understood that the study area as discussed under the region’s geology is susceptible to liquefaction. The geotechnical data largely support the geologic-based liquefaction susceptibility of the study area.