The 2011 M9.0 off the Pacific Coast of Tohoku Earthquake (Tohoku-oki earthquake) brought a great impact on the long-term forecasting of subduction earthquakes around the Japanese islands. Short historic data together with dogmas of modern seismology, such as conventional asperity model, characteristic earthquake model, and earthquake scaling law prevented us to have anticipated the size of M9 earthquake offshore Pacific coast of Tohoku. It may suggest that longer than 1000-year earthquake occurrence history is required to properly evaluate the size and frequency of mega-thrust events, same as the M~7 destructive earthquakes associated with inland active faults. The Tohoku-oki earthquake has significantly changed the state of crustal stress in northeast Honshu island from EW compression to EW extension, in which numerous widespread triggered earthquakes have been occurring. Here I introduce the coseismic stress transfer due to the Tohoku-oki earthquake onto the major active faults, and then demonstrate the importance of the transient changes of state of stress on the faults for long-term earthquake forecasting during the next few decades.

抄録全体を表示

A undersea earthquake with a magnitude of 9.0 "The 2011 off the Pacific Coast of Tohoku earthquake" took place off the Pacific coast of Japan at 14:46 JST (5:46 UTC) on March 11, 2011. A massive tsunami caused by the earthquake struck the Pacific side of Japan, especially the coasts of Aomori, Iwate and Miyagi prefectures, resulting in a cataclysmic disaster "East Japan Great Earthquake Disaster (Higashi Nihon Daishinsai in Japanese)". This paper describes the fundamental characteristics of Tsunami and the brief overview of the past huge tsunami disasters in Sanriku area. The tsunami damages of the East Japan Great Earthquake Disaster are, furthermore, reported on the base of the field survey, which was conducted from April 4 to 9, 2011 as a group of the 2011 Tohoku Earthquake Tsunami Joint Survey Group of Japan.

抄録全体を表示

At 14:46 local time on March 11, 2011, a magnitude 9.0 earthquake occurred off the coast of northeast Japan. This earthquake generated a tsunami that struck Japan as well as various locations around the Pacific Ocean. With the participation of about 300 researchers from throughout Japan, joint research groups conducted a tsunami survey along a 2,000 km stretch of the Japanese coast. The inundation height and run-up height were surveyed by laser, GPS and other instruments. Based on the survey dataset, the regional and local scale analyses were conducted to understand the basic characteristics of this event. The survey data are shown with photograph and are discussed about magnitude of damage and tsunami event.

抄録全体を表示

On March 11, 2011, at 14:46 local time, a powerful earthquake occurred off the Sanriku coast of northeastern Japan. It was immediately apparent that this was the strongest earthquake on the historical record, and the resulting series of tsunami ravaged the Tohoku region. In Iwate Prefecture, the tsunami height generally exceeded the design tsunami level for safety, which had been determined on the basis of the Meiji-Sanriku tsunami (1896), the Showa-Sanriku tsunami (1933), and the Chile tsunami (1960). As of Jan. 30, the number of dead and missing in Iwate rose to 5993. Over 24,000 buildings had been destroyed. After the Showa-Sanriku, disaster prevention facilities were built along the coast. However, many tsunami seawalls and water gates suffered enormous damage from the impact of the 2011 Tohoku Tsunami. This paper sketches out the characteristics and scope of the damage in the coastal areas of Iwate Prefecture.

抄録全体を表示

In Iwate, Miyagi and Fukushima Prefectures, more than 1,000 people were killed or missing each due to the 2011 off the Pacific coast of Tohoku Earthquake and Tsunami. It is thought that damaged local governments have faced a lot of difficult problems concerning social responses caused by the wide-area catastrophic damage. The purpose of my paper was to examine problems concerning social responses under the Great East Japan Earthquake Disaster that are peculiar to “a wide-area catastrophic disaster". I define “a wide-area catastrophic disaster" to refer to a disaster that causes catastrophic damage to two more prefectures. For the purpose of this study, first, the method of disaster categorization in terms of the degree of damage and the extent of damage was proposed. Secondly, the degree of damage and the extent of damage of the 2011 event were discussed in terms of tsunami height, inundation area, the number of dead and missing people and the amount of disaster debris. Thirdly, particular problems concerning social responses under the 2011 event were discussed by using limited reports and data that are published on the Internet. As a result, 5 types of particular problems under the 2011 event as a wide-area catastrophic disaster were pointed out: the limit of social response of damaged local governments, the limit of social response of supporting local governments, competition of resource support during damaged local governments, instability of policies, uncertainty of problem concerning social response. In conclusion, understanding the particular problems concerning social response under a wide-area catastrophic disaster is considered essential for reducing damages of next catastrophic disasters. It is recommended that particular problems concerning social responses under the 2011 event are discussed by using more data that will be published and hearing the local governors in the damaged area and so on.

抄録全体を表示

This study experimentally examined the spouting phenomenon of the cohesive powder from an orifice when air was supplied from the top and the bottom of powder bed in a vessel. The stable discharge of the cohesive powder was obtained as the same flow rate of air was simultaneously supplied at the top and the bottom of the powder bed. Then, it was observed that the flow pattern of powder bed in a vessel became a mass flow, and that the discharged powder jet from an orifice was dispersed in the atmosphere. It was found that the interstitial air pressure affected the change of the void fraction and the discharge coefficient. In addition, it was confirmed that the interstitial air pressure during the spouting of powder greatly influenced the mass flow rate of powder through an orifice.

抄録全体を表示

For the purpose of direct simulations of gas entrainment (GE) phenomenon in fast reactors, the authors are developing a high-precision simulation algorithm for gas-liquid two-phase flows on non-orthogonal meshes. In the algorithm, the high-precision volume-of-fluid (PLIC-VOF) algorithm is employed to simulate interfacial dynamic behaviors. However, the calculation of an interface normal is not accurate enough to reproduce any rectilinear interfaces, i.e. the accuracy of the calculation is at most 1st-order. In this paper, the calculation method for an interface normal is improved by developing a height function algorithm on non-orthogonal meshes. As a result of basic verification, the height function algorithm succeeds in reproducing rectilinear interfaces on a non-orthogonal triangular mesh. In addition, an interfacial curvature is calculated accurately based on the interface normal calculated by the height function algorithm. Therefore, it is confirmed that the developed height function algorithm can enhance the simulation accuracy of gas-liquid two-phase flows.

抄録全体を表示

Behaviors of air bubbles undergoing collisions with a free surface / rigid wall are numerically studied for various viscosities and surface tensions. The moving boundary problem is solved by means of a front-tracking method to correctly capture an exchange between the surface and kinetic energies in the bouncing process. As found in experiments by Legendre et al. (2005, Phys. Fluids, 17: 097105), the simulated contact time during the bounce normalized by the initial bubble radius and the rise velocity is proportional to the square root of the Weber number, supporting the validity of the mass-spring model proposed by Legendre et al.(2005). For the bubble-rigid wall system, the relation between the restitution coefficient (i.e. the ratio of the rebound bubble velocity to the rise velocity) and Ca/St (here, Ca is the capillary number and St is the Stokes number) is consistent with the experiments and the theoretical model of Zenit and Legendre (2009, Phys. Fluids, 21: 083306). The restitution coefficient of the bubble-free surface system is found to be larger than that of the bubble-rigid wall system, implying the smaller viscous dissipation during the bounce, as a result of the smaller vorticity generation on the free surface.

抄録全体を表示