Rupture process of the 2011 Tohoku earthquake from the joint inversion of teleseismic and GPS data

Teleseismic and GPS data were jointly inverted for the rupture process of the 2011 Tohoku earthquake. The inversion results show that it is a bilateral rupture event with an average rupture velocity less than 2.0 km/s along the fault strike direction. The source rupture process consists of three sub-events, the first oc- curred near the hypocenter and the rest two ruptured along the up-dip direction and broke the sea bed, causing a maximum slip of about 30 m. The large-scale sea bed breakage may account for the tremendous tsunami disaster which resulted in most of the death and missing in this mega earthquake.

Earthquake engineering research needs in light of lessons learned from the 2011 Tohoku earthquake

Earthquake engineering research and development have received much attention since the first half of the twentieth century. This valuable research presented a huge step forward in understanding earthquake hazard mitigation,which resulted in appreciable reduction of the effects of past earthquakes. Nevertheless,the 2011 Tohoku earthquake and the subsequent tsunami resulted in major damage. This paper presents the timeline of earthquake mitigation and recovery,as seen by the authors. Possible research directions where the authors think that many open questions still remain are identified. These are primarily based on the important lessons learned from the 2011 Tohoku earthquake.

Spatio-temporal characteristics of aftershocks and seismogenic structure of the 2011 Mw9.0 Tohoku earthquake,Japan

The Tohoku megathrust earthquake, which occurred on March 11, 2011 and had an epicenter that was 70 km east of Tohoku, Japan, resulted in an estimated ten′s of billions of dollars in damage and a death toll of more than 15 thousand lives, yet few studies have documented key spatio-temporal seismogenic characteristics. Specifically, the temporal decay of aftershock activity, the number of strong aftershocks (with magnitudes greater than or equal to 7.0), the magnitude of the greatest aftershock, and area of possible aftershocks. Forecasted results from this study are based on Gutenberg-Richter’s relation, Bath’s law, Omori’s law, and Well’s relation of rupture scale utilizing the magnitude and statistical parameters of earthquakes in USA and China (Landers, Northridge, Hector Mine, San Simeon and Wenchuan earthquakes). The number of strong aftershocks, the parameters of Gutenberg-Richter’s relation, and the modified form of Omori’s law are confirmed based on the aftershock sequence data from the Mw9.0 Tohoku earthquake. Moreover, for a large earthquake, the seismogenic structure could be a fault, a fault system, or an intersection of several faults. The seismogenic structure of the earthquake suggests that the event occurred on a thrust fault near the Japan trench within the overriding plate that subsequently triggered three or more active faults producing large aftershocks.

Analysis of the co-seismic responses of the fluid well pattern system in Jiangsu Province to the Wenchuan and Tohoku earthquakes

This thesis discusses the earthquake reflecting ability of the observation well pattern system of Jiangsu Province, China, which has been digitally renovated, and probes into the cause of the major differences in the earthquake reflecting abilities of well holes at different measurement points. This is achieved through the analysis of the co-seismic responses to the Wenchuan (2008; Ms8.0, China) and Tohoku (2011; Ms9.0, Japan) earthquakes. We found that the co-seismic response of water level from regional well holes in Jiangsu Province was stronger than that of water temperature. The water-level co-seismic response follows a consistent law and is closely related to the earthquake magnitude. The co-seismic response of water temperature strongly varied among well points, and was more often manifested as a slow restorative change. The co-seismic responses also varied based on tectonic elements. The response in central and northern Jiangsu was weaker than that of southern Jiangsu, possibly due to the thicker loess cover layer in central Jiangsu which makes it less effective at capturing the micro-changes of stress-strain states relative to the hilly land in the south. The more complicated geological structure in southern Jiangsu makes it contribute to greater changes in the state of underground water after a minor disturbance.

Slotted Hole Effect on Damage Mechanism of Gymnasium Building with RC Frame and Steel Roof

On the 2011 off the Pacific Coast of Tohoku Earthquake, gymnasium buildings exhibited the unexpected structural damages, which prevented a use as evacuation shelters in during- and post-disaster periods. The major failure occurring on the connection between the RC column top and steel roof as well as the cracks in the RC column base was observed during the emergent inspection. According to the earlier studies, it was implied that the presence of the slotted hole possibly deteriorates the seismic capacity;however, the length of slotted hole was fixed at a certain value. Facing this concern, this research attempts to clarify the influence of the slotted hole length through a comprehensive parametric study by pushover and seismic response analyses. In conclusion, it has been discovered that the slotted hole deteriorates the seismic capacity for the connection failure up to almost 50% of that without slotted hole. Moreover, the discrepancy of characteristics obtained by the static and dynamic analyses is originated by means of the presence of slotted hole. This slotted hole effect should be noted by structural engineers and researchers to provide the adequate seismic diagnosis and strengthening.

Increasing spatial coverage in rough terrain and vegetated areas using InSAR optimized pixel selection:application to Tohoku,Japan

One of the major limitations of using Interferometric Synthetic Aperture Radar(InSAR)in time series analysis is the low-phase coherence associated with rough terrain and vegetated areas,which results in limited spatial coverage in such regions.Permanent scatterers technique was introduced to overcome this limitation using time-series analysis.However,identifying major scatterers within a pixel requires the single-looked pixels oversampling which can be a demanding process especially with large interferometric stacks and vast study areas.Therefore,using multilooked temporal coherent pixels was proposed to increase processing efficiency and coverage by utilizing distributed targets,but this technique may exclude pixels with reliable phase returns because of their temporal varying neighboring pixels.In this paper,we propose a technique to identify multilooked temporal stable pixels with reliable phase returns independent of their neighboring pixels.We conduct a simulation analysis to relate the spatial coherence of a pixel with its expected temporal correlation in the time series analysis module.We found that a liberal temporal correlation threshold of 0.53 in multilooked pixels stack is equivalent to a spatial coherence threshold of 0.2 when using number of looks of 9,which is considered acceptable in temporal coherent pixels,in terms of phase standard deviation.Applying these findings to study the 2011 Tohoku earthquake in the northeastern part of Japan resulted in increasing the number of usable pixels and spatial coverage index by nearly 50.4%and 36.8%,respectively,compared to the temporal coherent pixels.Furthermore,we propose an approach to integrate GPS observations with InSAR time series analysis,which resulted in deformation maps of the megathrust 2011 Tohoku earthquake with mean RMSE of 11.4 mm and a correlation of 98%in comparison to GPS observations.