Lessons Learned from the 2011 Great East Japan Tsunami: Performance of Tsunami Countermeasures, Coastal Buildings, and Tsunami Evacuation in Japan

In 2011, Japan was hit by a tsunami that was generated by the greatest earthquake in its history. The first tsunami warning was announced 3 min after the earthquake, as is normal, but failed to estimate the actual tsunami height. Most of the structural countermeasures were not designed for the huge tsunami that was generated by the magnitude M = 9.0 earthquake; as a result, many were destroyed and did not stop the tsunami. These structures included breakwaters, seawalls, water gates, and control forests. In this paper we discuss the performance of these countermeasures, and the mechanisms by which they were damaged; we also discuss damage to residential houses, commercial and public buildings, and evacuation buildings. Some topics regarding tsunami awareness and mitigation are discussed. The failures of structural defenses are a reminder that structural (hard) measures alone were not sufficient to protect people and buildings from a major disaster such as this. These defenses might be able to reduce the impact but should be designed so that they can survive even if the tsunami flows over them. Coastal residents should also understand the function and limit of the hard measures. For this purpose, non-structural (soft) measures, for example experience and awareness, are very important for promoting rapid evacuation in the event of a tsunami. An adequate communication system for tsunami warning messages and more evacuation shelters with evacuation routes in good condition might support a safe evacuation process. The combination of both hard and soft measures is very important for reducing the loss caused by a major tsunami. This tsunami has taught us that natural disasters can occur repeatedly and that their scale is sometimes larger than expected.     

C, O, S and Sr isotope studies on the genesis of Fe-carbonate and barite mineralizations in the Attepe iron district (Adana, Southern Turkey)

The Attepe district consists of Precambrian, Lower–Middle Cambrian, Upper Cambrian–Lower Ordovician and Mesozoic formations. It contains several iron deposits and occurrences. Three types of iron-mineralizations can be distinguished in the area; (i) Sedimentary Fe-sulfide in Precambrian bituminous metapelitic rocks, and Fe-oxides in Precambrian metasandstones (SISO), (ii) vein-type Fe-carbonate and oxides composed of mainly siderite, ankerite and hematite including barite in Lower–Middle Cambrian metacarbonates of the Çaltepe Formation (HICO), (iii) karstic Fe-oxides and hydroxides essentially in the Lower–Middle Cambrian metacarbonates and the unweathered Fe-carbonates (KIO). The latter type is more widespread and located at the upper parts of the most important mineable iron deposits like Attepe deposit.

Oxygen-, carbon-, sulfur- and strontium-isotope studies have been performed on siderites and barites in the vein-type ores, and on calcites in the recrystallized Çaltepe Limestones to investigate the sources and formation mechanism of primary ore-forming constituents. The δ¹³C values of siderites and calcites in limestones of the Çaltepe Formation range from −10.10‰ to −8.20‰, and from −0.8‰ to 2.30‰. Both carbonate minerals show δ¹⁸O values between 17.50–18.30‰ and 16.20–23.00‰, respectively. The δ¹³C and δ¹⁸O isotopic variations do not indicate any direct or linear relations between siderites and limestones. However, it is possible that the carbon and oxygen isotopic compositions of carbonate minerals could be changed to some extent, when limestones were subjected to hydrothermal processes or thermal alterations during metamorphism.

The isotopic values of barites display 32.40–38.30‰ for δ³⁴S and 12.20–14.70‰ for δ¹⁸O. The strontium isotope ratios (0.717169–0.718601) of barites and the sulfur isotope compositions of barites and pyrites suggest that there are no direct linkages of ore-forming compounds neither with a magmatic source nor with sedimentary pyrite formations in the Precambrian bituminous shales of the Attepe formation.

According to the field observations and the stable isotope data, siderites and ankerites should be formed by interaction between iron-rich hydrothermal fluids and Çaltepe limestones, whereas isotope ratios of barites indicate that they were formed by mixing of sulfur-rich meteoric waters and deeply circulated hydrothermal solutions.     

Prediction of the unconfined compressive strength of compacted granular soils by using inference systems

Adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN) models have been extensively used to predict different soil properties in geotechnical applications. In this study, it was aimed to develop ANFIS and ANN models to predict the unconfined compressive strength (UCS) of compacted soils. For this purpose, 84 soil samples with different grain-size distribution compacted at optimum water content were subjected to the unconfined compressive tests to determine their UCS values. Many of the test results (for 64 samples) were used to train the ANFIS and the ANN models, and the rest of the experimental results (for 20 samples) were used to predict the UCS of compacted samples. To train these models, the clay content, fine silt content, coarse silt content, fine sand content, middle sand content, coarse sand content, and gravel content of the total soil mass were used as input data for these models. The UCS values of compacted soils were output data in these models. The ANFIS model results were compared with those of the ANN model and it was seen that the ANFIS model results were very encouraging. Consequently, the results of this study have important findings indicating reliable and simple prediction tools for the UCS of compacted soils.     

Lateral variations of the modal (a/b) values for the different regions of the world

Several catalogues of global earthquakes reported for the time period from 1900 to 2000 have been compiled to examine lateral variations of the modal (a/b) values as derived from the Gutenberg–Richter empirical law. For this purpose, the world was divided into 27 different seismic regions in terms of tectonic environments. The parameters a and b were calculated using the least-squares method. The modal values computed for each region were used to produce a global map of the modal values using a grid space of 3°. The results show that a and b-values do not always supply much information about tectonic environments of the different regions. It is observed that the modal values estimated for different tectonic regions are consistent with seismicity of the world and represent global seismic sources better than a or b values. The highest modal values have been found in the oceanic subduction zones, and the lowest values in the oceanic ridges. Lowest b values are observed in trenches. These observations suggest that there is a correlation between apparent stresses and b values. Mapping of the modal values provides detailed images of the zones presenting low and high seismic activity and it may be used as a measure of seismic potential sources and relative hazard levels.     

Historical earthquake activity of the northern part of the Dead Sea Fault Zone, southern Turkey

The northern part of the Dead Sea Fault Zone is one of the major active neotectonic structures of Turkey. The main trace of the fault zone (called Hacıpaşa fault) is mapped in detail in Turkey on the basis of morphological and geological evidence such as offset creeks, fault surfaces, shutter ridges and linear escarpments. Three trenches were opened on the investigated part of the fault zone. Trench studies provided evidence for 3 historical earthquakes and comparing trench data with historical earthquake records showed that these earthquakes occurred in 859 AD, 1408 and 1872. Field evidence, palaeoseismological studies and historical earthquake records indicate that the Hacıpaşa fault takes the significant amount of slip in the northern part of the Dead Sea Fault Zone in Turkey. On the basis of palaeoseismological evidence, it is suggested that the recurrence interval for surface faulting event is 506 ± 42 years on the Hacıpaşa fault.     

Modeling and simulating earthquake accelerograms using strong-motion data from the Istanbul, Turkey, region

In order to simulate earthquake ground motions for the Instanbul (Turkey) region, acceleration time series from western Turkey are modeled by transforming the series into a stationary one which can be described by an autoregressive moving-average (ARMA) process. The ARMA and other parameters used in the stationary transformation are related to physical parameters (e.g. magnitude, distance to epicenter, depth to hypocenter and duration) via a regression analysis. To create simulations for a given set of physical parameters, the modelling procedure is reversed.     

Relation of tectonic structure to groundwater flow in the Beypazari region, NW Anatolia, Turkey

The Beypazari region in NW Anatolia (Turkey) is characterized by high water demand and stress on available water resources. Tectonic structures control the groundwater flow, hydraulic head and well yield in the study area, which is located in the central part of the Beypazari Neogen basin. The impact of major tectonic structures on groundwater flow in the Cakiloba-Karadoruk aquifer is described. This aquifer is of sedimentary composition and underwent tectonic deformation, post-Miocene, forming northeast-striking asymmetric synclines, anticlines, monoclines, high-angle reverse faults and N–S striking tensional faults. Some of these structures affect groundwater flow by separating the aquifer system into sub-compartments, each having unique recharge, boundary and flow conditions. The groundwater system is compartmentalized into three sub-systems under the impacts of the Zaviye and Kanliceviz faults: (1) Arisekisi, (2) Elmabeli and (3) Southern sub-systems. The southern part of the Arisekisi sub-system and the Southern sub-system are characterized by a syncline and the aquifer is confined in the central part of the syncline. The Elmabeli sub-system has unconfined conditions. Consequently, the effects of tectonic structures are shown to be important for selecting well locations, evaluating groundwater use, groundwater management, and contaminant control in the study area, and also in other tectonic regions.