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In 2011, Japan received a massive blow from the Tohoku Earthquake and the ensuing disaster at the Fukushima Dai-ichi Nuclear Power Generation Plant (hereafter, the Fukushima Nuclear Plant), with 18,000 people dead or missing, and more than 330,000 evacuated long-term. Anxiety among the people of Japan concerning earthquakes and nuclear accidents is higher than ever, but other hazards confront them as well. This research investigated whether the Japanese people’s anxiety about a variety of other hazards has increased or decreased since the Tohoku Earthquake. Based on the availability heuristic, the contrast effect, and the finite-pool-of-worry hypothesis, it was predicted that public anxiety about earthquakes and nuclear accidents would increase, but anxiety about other hazards would decrease. Data from two nationwide surveys conducted in January 2008 and January 2012 were compared to see the change in societal levels of anxiety toward 51 types of hazards. The results showed that anxiety had increased afte...

The 2011 Tohoku earthquake caused about 19,000 casualties, dead and missing, of which most resulted from the enormous subsequent tsunami. Those who survived the tsunami had evacuated to higher ground, their action reflecting the importance of public judgment in mitigating the disaster. In this study, we examined the change in the risk assessment of tsunami heights since the 2011 Tohoku earthquake among residents in western Japan, an area that was not affected by the earthquake but that has long been at risk for such natural disasters. While existing research argues that the experience of natural disasters increases the public's alertness, the results of our survey (N=733 at pre-quake and N=1036 at post-quake) showed that, after the earthquake, those who live in this area had augmented their estimations of what tsunami heights are dangerous enough to warrant evacuation. Laypersons are highly inclined to make judgments based on the numbers first presented to them. This adjustment and anchoring heuristic well explains these paradoxical results. The vast amount of media coverage of the record-breaking tsunami established an anchor and prompted people to elevate the evacuation height, altering their judgments in the direction of greater vulnerability. Considering the difficulty of subsequent adjustments, our findings indicate the importance of conveying basic information about the risks of lesser intensity natural disasters in the initial stages of reporting a record-breaking disaster to those who have not directly experienced one.

SUMMARY A long-term seismic array observation was conducted around the North Mariana island arc using 10 long-term ocean bottom seismometer (LTOBS), which gathered data for one year starting in 2001 October. The purpose of the observation was to research the deep seismic activity and the structure of the Mariana subduction system. By using data from nine of the LTOBS, which covered about 11 months of elapsed time, more than 3000 local events were found through the hypocentre determination with a one-dimensional velocity model. Only 59 of these events were listed in the same period on the US National Earthquake Information Centre’s Preliminary Determination of Epicentres (PDE) publication. The hypocentres with small determination errors clearly show a double seismic zone (DSZ) reaching 150km in depth with two seismic planes separated by about 30km. The extension of the DSZ’s seismic activityremainshighuntiladepthofabout 270km.Inthebackarc basin,someshallowseismic activitieswerefoundaslinearfociaroundthecurrentridgeaxis.Highseismicactivitywasalso recorded to the north and the west of a large serpentine seamount in the forearc. In addition, a zone almost devoid of earthquakes exists in the upper plane of the DSZ with the low velocity of the P phase (VP) region modelled by an inversion. This region looks like a narrow channel running east to west. A shear wave splitting study of the area indicates a change of splitting direction near the southern edge of this channel. A result of a gravity study also shows negative gravity anomalies in the same area. This region could be a serpentinized forearc mantle with watersuppliedtoitfromaseamountthatwasinthepastcarrieddownwardswiththesubducting

[1] We describe a new one-dimensional Q model for short-period body waves derived from a data set of 15,000 differential t* measurements of teleseismic P and S waves recorded in broadband seismograms. Measured t* values are little affected by the source time function or instrument response since the P and S waves are recorded at the same station from the same event. We process the data using a waveform cross-correlation method applied to the first half cycle of the waveforms to avoid reflection and conversion effects. We invert our t* measurements for a two-layer QS model. Our new Q model has about the same attenuation in the upper mantle and less attenuation in the lower mantle than models derived from longer period data sets. This implies that the frequency dependence of Q is more apparent in the lower mantle and that the effects of attenuation in the upper mantle are approximately constant at frequencies below about 1 Hz. We also observe lateral variations of attenuation in the uppermost mantle by solving for station and event terms, which exhibit correlations with regional tectonics.

[1] We obtained three-dimensional (3-D) shear wave speed structure beneath the Philippine Sea and the surrounding region from seismograms recorded by land-based and long-term broadband ocean bottom seismographic stations. The ocean bottom data gave us a better station coverage to obtain a higher spatial resolution (about 300–400 km) in the Philippine Sea than in previous studies. We employed a new technique of surface wave tomography, in which multimode phase speeds are measured and inverted for a 3-D shear wave speed structure by incorporating the effects of finite frequency and ray bending. There is a sharp speed contrast along the Izu-Bonin-Mariana trench, across which the Philippine Sea side has a significantly slower upper mantle than the Pacific Ocean side. In the upper 120 km, the shear wave speed structure is well correlated with the age of the provinces. At depths greater than 160 km, the pattern is dominated by fast anomalies of the subducted slabs of the Pacific plate and two slow anomalies to the south of the Daito ridge and in the southernmost part of the Philippine Sea.

The purpose of this study was to evaluate the usefulness of a novel method of detecting tuberculosis infection, QuantiFERON TB-2G (QFT), in a large scale contact investigation when an outbreak of mass tuberculosis infection was suspected.The index case was a health-care worker who worked in a maternity hospital. The investigated contacts were categorized as follow according to the grade of closeness of contact; the "very close" contact group (11 subjects), the "close" contact group (33 subjects), and the "non-close" contact group (3,791 subjects). For the former two groups, tuberculin skin test (TST), chest X-ray examination and QFT were conducted. For the last contact group, TST and chest X-ray examination were conducted only to subjects who aged less than 29 years old, while only chest X-ray examination was conducted to those aged 30 years or older. The QFT test, i.e., a whole blood interferon-gamma assay using Mycobacterium tuberculosis-specific antigens, was performed to the "very close" and "close" contacts, and for strong tuberculin reactors among the "non-close" contacts.The number of infected subjects in the "very close" contact group, the "close" contact group, and the "non-close" contact group were 7, 7, and 277, respectively, based on TST results. On the other hand, the number of infected subjects in each group were 3, 2, and 5, respectively, based on the QFT test.If the indication of chemoprophylaxis was determined based on TST test, this case would have been regarded a large tuberculosis outbreak. However, the use of the QFT test greatly reduced the number of the infected persons, so that the possibility of such massive TB outbreak was denied. Thus, the use of QFT, with which TB infection could be detected more accurately, seems to be very beneficial in contact investigations.

[1] Anelasticity of the Earth causes physical dispersion of seismic waves. The appropriate choice of reference frequency is important to determine arrival times of body waves, especially later arrival times, from broadband seismograms by fitting observed to synthetic waveforms. Our question is how to choose the reference frequency of physical dispersion, f0, consistent with the extensive data sets of hand-picked body wave arrival times compiled through the long history of seismology. Setting the reference frequency to be the conventional 1 Hz, we measured S-P differential travel times by waveform fitting. We found a systematic discrepancy between the measured and hand-picked S-P times that can be removed by changing f0 from 1 to 2 Hz. This change of f0 requires a correction in Q of the PREM model: (1) if Q is strictly frequency-independent, we need a 15% increase in Q value or (2) if Q is fixed to the value given by PREM at a period of 200 s, we need to introduce a small frequency dependence in Q, where the dependence is expressed by the power law with an exponent of 0.04.

We have examined the rupture process of the 2010 Yushu, China, earthquake, which occurred in the eastern Tibetan plateau. Based on the results of centroid location grid searches, the aftershock distribution, and InSAR observations, we first constructed a left-lateral strike-slip bending fault model. We then carried out joint inversions of the teleseismic waveform data and InSAR data using various rupture front velocities. We obtained the optimum source model with a seismic moment of 2.3 × 1019 N m (Mw ∼ 6.8), where the rupture velocity was found to be slightly faster than the shear wave velocity of the crust in this region. This supershear rupture velocity resulted in severe damage in and around the county seat of Yushu, which is located in the forward rupture direction of the source model. The features of this event, such as the shallow and fast rupture propagation may represent a seismic feature of the tectonic activity in the eastern Tibetan plateau.