Great Tohoku earthquake of March 11, 2011: Preliminary seismological analysis

The results of a preliminary analysis of the source zone of the 2011 Tohoku earthquake (M _w = 9.1) near the east coast of Honshu, Japan, are considered. We traced the seismic history of the release of the cumulative scalar seismic moment for the last 110 years and temporal variations in the ordering index for the last 35 years. These parameters are important characteristics of a seismotectonic deformation process. The foreshock activation stage and the initial phase of the aftershock process are studied based on these characteristics.     

The influence of the Kuril Islands on the penetration of tsunamis into the Sea of Okhotsk (on the example of the Japan tsunami on March 11, 2011)

The features of the propagation of the tsunami of March 11, 2011 in the northeastern Pacific have been studied with the aim of revealing the degree of influence of the Kuril Islands on the penetration of the tsunami in the Sea of Okhotsk. For this, a series of computational experiments have been performed within the shallow water theory using bathymetry (1) with and (2) without the Kuril Islands. The wave heights calculated have been analyzed, and the tsunami’s magnitude and intensity in the Sea of Okhotsk have been estimated. The computational experiments performed allow assessment of a decrease in the tsunami intensity while passing the Kuril Islands.     

Specific features of the appearance of seismotectonic deformations during the genesis of March 11, 2011, Tohoku earthquake source

The results of investigating the preparation zone of the catastrophic earthquake of March 11, 2011, near the eastern coast of Honshu Island are presented. A retrospective analysis of the focal mechanisms of deep earthquakes in the western part of the Pacific Ocean made it possible to reveal their influence on the zone of the Tohoku earthquake source. The preparation of this earthquake is also investigated within an analysis of the seismotectonic deformation processes at the regional level, which includes an estimation of the temporal trends of some key parameters, as well as the detection of their variations and the spatial confinement of anomalies to the source zone.     

Characteristics of the Short-Period S-Wave Attenuation Field in the Source Zone of the Strongest Tohoku Earthquake of March 11, 2011 (Mw = 9.0)

Izvestiya, Atmospheric and Oceanic Physics - The characteristics of the short-period S-wave attenuation field in the source zone of the strongest Tohoku earthquake of March 11, 2011 in the...     

Propagation Mechanisms of Incident Tsunami Wave in Jiangsu Coastal Area, Caused by Eastern Japan Earthquake on March 11, 2011

At 13:46 on March 11, 2011 (Beijing time), an earthquake of Mw=9.0 occurred in Japan. By comparing the tsunami data from Guanhekou marine station with other tsunami wave observation gathered from southeast coastal area of China, it was evident that, only in Guanhekou, the position of the maximum wave height appeared in the middle part rather than in the front of the tsunami wave train. A numerical model of tsunami propagation based on 2-D nonlinear shallow water equations was built to study the impact range and main causes of the special tsunami waveform discovered in Jiangsu coastal area. The results showed that nearly three-quarters of the Jiangsu coastal area, mainly comprised the part north of the radial sand ridges, reached its maximum tsunami wave height in the middle part of the wave train. The main cause of the special waveform was the special underwater topography condition of the Yellow Sea and the East China Sea area, which influenced the tsunami propagation and waveform significantly. Although land boundary reflection brought an effect on the position of the maximum wave height to a certain extent, as the limits of the incident waveform and distances between the observation points and shore, it was not the dominant influence factor of the special waveform. Coriolis force’s impact on the tsunami waves was so weak that it was not the main cause for the special phenomenon in Jiangsu coastal area. The study reminds us that the most destructive wave might not appear in the first one in tsunami wave train.     

日本“3·11”海啸引起的乐清湾共振研究

本文基于TELEMAC-2D模型建立太平洋区域海啸传播模型,模拟2011年日本“3·11”海啸事件下海啸波的传播。使用实测数据对该模型进行验证,在模型验证良好的基础上分析日本“3·11”海啸事件对乐清湾的影响。通过频谱分析得到“3·11”海啸激发的乐清湾内240、180和103 min这3个主导模态的幅值及其相位。通过白噪声实验对乐清湾的固有共振特征进行估算,进一步支持了乐清湾在上述3个模态发生共振这一结论。白噪声实验还表明,海啸等海洋灾害发生时会在乐清湾湾顶及湾口处产生较大的增水,该结论对乐清湾内海洋灾害风险防范具有指导意义。     

Great Japan earthquake of March 11, 2011: Tectonic and seismological aspects

The tectonic and seismological aspects of the Great Japan Earthquake, which occurred on March 11, 2011 (M _w = 9.0), at the Pacific margin of the northeastern part of Honshu Island, are discussed. The structure and seismotectonic data, seismicity, and the reccurence rate of the great (M ≥ 7.6) earthquakes throughout history and in modern times are represented. It is shown that the reccurence rate of the great events is about 40 years, and that of megaearthquakes is 1000 years or more. A seismic gap of about 800 km in length is found in the region under study, located to the south of latitude 39° N and full of aftershocks to the megaearthquake of March 11, 2011. This event is probably connected with the deep thrust along the Benioff zone and its structural front (Oyashio nappe at the middle Pacific continental slope). The aftershock sequences of this megaearthquake and the Sumatra-Andaman (2004) megaearthquake are compared. It is found that several of their key characteristics (the number of aftershocks, the magnitude of the strongest aftershock, and the time of its occurrence) for 25 days are comparable for both cases with a significant difference in the energies of aftershock processes. A probable scenario for the origination of a repeated shock with M ∼ 8.0 in the Japan Trench is discussed.     

Megaearthquake of March 11, 2011, in Japan: The event magnitude and the character of the aftershock sequence

The great Japanese earthquake (GJE) of March 11, 2011, was a megaevent. The conditions under which such seismic catastrophes occurred are discussed. The regime of the aftershocks of this megaevent is compared with the data on the aftershock sequences which accompanied the Simushir earthquakes (2006 and 2007) and the Andaman earthquake (2004) and with the seismicity behavior in the generalized vicinity of a strong earthquake. The aftershock sequences of the abovementioned strong earthquakes are shown to represent the sets of trend changes in the postshock activity and specific outbursts of seismic activity. Activity outbursts are characterized not only by an increase in the number and energy of events, but also by a decrease in the recurrence plot slope (b value) and the average earthquake depth. Some such outbursts correspond to the occurrence of strong repeated shocks. A possible mechanism for outbursts of seismic activity is proposed. The possibility of a stronger repeated shock in the vicinity of the megaearthquake of March 11, 2011, is discussed.     

Metal accumulation in mussels of the Kuril Islands, north-west Pacific Ocean

Concentrations of cadmium, copper, iron, lead, manganese, nickel and zinc were investigated in two species of mussel from the Kuril Islands in the north-western Pacific Ocean: the short-lived mussel Mytilus trossulus and the much larger and longer-lived Crenomytilus grayanus. The concentrations of most elements were low, and these reported levels are believed to reflect background values for pristine locations. However, both iron and zinc concentrations were elevated in some samples taken from areas of hydrothermal vent activity, and these are believed to reflect the enrichment of the two metals in solution at such sites. Furthermore, the concentrations of cadmium were unusually elevated in both species of mussel, especially in the longer-lived C. grayanus. The high accumulation of cadmium in mussels from the Kuril Islands is believed to reflect regional upwelling, but it is also postulated that filtration rates of the mussels are high due to low levels of suspended matter, and this leads to a high assimilation efficiency for cadmium. The distribution of cadmium amongst the tissues of C. grayanus is also reported, and the need for further ecotoxicological studies in the area is proposed.     

Seismic catastrophe in Japan on March 11, 2011: Long-term prediction on the basis of low-frequency microseisms

This paper presents a software technique for analyzing the multidimensional time series of microseismic oscillations on the basis of over 14 years of continuous observations, from early 1997 to February 2011, at F-net (Japan) broadband seismic stations. An analysis of the multifractal parameters of low-frequency microseismic noise allowed us to hypothesize, in as early as 2008, that Japanese Islands were approaching a large seismic catastrophe, the signature of which was a statistically significant decrease in the support width of the multifractal singularity spectrum. Subsequently, as new data became available and after some new statistics of microseismic noise (such as a logarithm of noise variance and an index of linear predictability) were included in joint analysis, we obtained some new results, indicating the facts that the parameters of the microseismic background had been increasingly synchronized (the synchronization process was estimated to start in mid-2002) and that the seismic danger had permanently grown. A cluster analysis of background parameters led us to conclude that in mid-2010 the islands of Japan entered a critically dangerous developmental phase of seismic process. The prediction of the catastrophe, first in terms of approximate magnitude (mid-2008) and then in terms of approximate time (mid-2010), was documented in advance in a series of papers and in proceedings at international conferences.     

Drifter Observations of Anticyclonic Eddies near Bussol' Strait, the Kuril Islands

Hydrographic surveys and satellite imaging reveal that mesoscale anticyclonic (AC) eddies are common features of the area south of Bussol' Strait, the deepest of the Kuril straits connecting the western North Pacific and Sea of Okhotsk. To examine the velocity structure of these eddies, we deployed groups of 15-m drogued satellite-tracked surface drifters over the Kuril-Kamchatka Trench in the fall of 1990 and late summer of 1993. Drifters in both groups entered large AC eddies centered over the axis of the trench seaward of Bussol' Strait and subsequently underwent a slow northeastward translation. One drifter (Drifter 1315) deployed near the center of the “Bussol' eddy” in 1990, remained in the eddy for roughly 45 days and made five loops at successively greater distances from the eddy center. Large-amplitude (80–100 cm/s) storm-generated inertial oscillations were observed during the first two loops. The vorticity field associated with the eddy resulted in a Doppler “red-shift” of inertial frequency motions such that the “effective” inertial period of 21 hours was roughly 4 hours greater than the nominal inertial period for the drifter latitude (45°N). In 1993, a second drifter (Drifter 15371) was retained in the Bussol' eddy for about 40 days. This eddy had characteristics similar to those of the 1990 eddy but was devoid of significant high-frequency motions until the drifter's final half loop. The observed spatial scales, persistence, and slow poleward translation of the eddies suggests that they play an important role in the dynamics of the East Kamchatka and Oyashio current systems. This revised version was published online in August 2006 with corrections to the Cover Date.     

Environmental impact of the powerful eruption of Sarychev Peak volcano (Kuril Islands, 2009) according to satellite imagery

The powerful Sarychev Peak eruption (Matua Island, Central Kuril Islands) in June 2009 is analyzed on the basis of remote sensing data (satellite images) and ground-based observations carried out in summer 2009. The nature of the eruption and catastrophic impact on ecosystems of the island is described.     

Ionospheric response to submarine earthquake of March 11, 2011, in Japan according to GPS observations

Using available Russian and international Global Positioning System (GPS) network data, we studied the ionospheric response to the M = 8.9 submarine earthquake of March 11, 2011, on the northeastern coast of Honshu Island, Japan, both near and far (about 2000 km away) from the epicenter. In the region over the epicenter, 8.7 min after the event, we detected a characteristic signal of the total electron content (TEC) variations consisting of compression and rarefaction phases and a linear transition zone in between, i.e., in the form of an N-type wave with a steep leading front indicating a rapid uplift of the water surface and, correspondingly, the bottom of the ocean. The shape of the signal can be used for early tsunami warning; i.e., it may indicate the tsunamigenic character of a submarine earthquake. We monitored the subsequent evolution of the ionospheric response as far as 2000 km from the epicenter. It was shown that, besides the wellknown ionospheric N-type wave response to the earthquake, there is also a response in the form of an inverted N-wave, both nearby and far from the epicenter. We detected two more types of ionospheric responses far from the epicenter: a solitary-like wave and an internal gravity wave (IGW). The detected signals have been interpreted.     

An outstanding achievement of the Russian Academy of Sciences: The successful forecast of the earthquake of March 11, 2011, in Japan

The seismic catastrophe in Japan was forecasted far ahead of time by scientists from the Russian Academy of Sciences. The most reliable forecast was made by A.A. Lyubushin, a leading researcher at the Schmidt Institute of Physics of the Earth. Over the 2008–2010 period, at a number of the most important international conferences, including that of the Seismological Society of Japan, Lyubushin warned that an earthquake with a magnitude of 8.5–9.0 could occur in Japan; it was published in English in leading scientific journals all over the world. On April 26, 2010, Lyubushin officially informed the Russian Advisory Council on Earthquake Prediction and Seismic Hazard Assessment of his forecast. One distinctive feature of this forecast is that it is based on large bodies of data on microseismic oscillations for the territory of Japan, which were mathematically treated using present-day methods. This forecast has a reliable physical justification and a visual interpretation. Brief information on the results of other Russian studies on the precursors of the main shock and aftershocks of the earthquake of March 11, 2011, in Japan is given.     

Sponge Communities in Three Submarine Caves of the Balearic Islands (Western Mediterranean): Adaptations and Faunistic Composition

Abstract. The sponge fauna of three neighbouring submarine caves of the Island of Majorca (Balcaric Islands) is studied along a light gradient; 45 species have been recorded and systematic data are given for those showing morphological, pigmentary, or spicule differences. Adaptation to darkness and precarious trophic conditions is also discussed.     

Conspicuous sediment structures in fossil beach deposits (southern Tenerife, Canary Islands, Spain): paleoliquefaction features versus biogenic origin

Tubular-shaped concretions and concretionary dykes occur in Holocene fossil beach deposits between the township of El Médano and Punta Roja in southern Tenerife, Canary Islands. These sediment structures have been interpreted either as the result of (a) the interaction between hot ignimbrites that overflowed wet beaches; (b) fast accumulation of beach sands on hot and degassing ignimbrites; (c) paleoliquefaction caused by an earthquake (seismites). Based on the interpretation as seismites, an intense paleoearthquake with a moment magnitude of M = 6.8 was proposed to be responsible for the generation of the paleoliquefaction structures. However, we here reinterpret the sedimentary structures in question using the general criteria diagnostic for rhizocretions and root tubules with respect to their orientation, size, branching system, and style of cementation and, thus, consider them, to be of biogenic origin.     

南海主要岛礁概率海啸风险评估

影响地震海啸的震源参数众多且具有很强的不确定性,充分评估海啸风险需要大量的情景模拟.本文基于建立的概率海啸风险模型,采用一种高效的海啸模拟方法,评估了南海主要岛礁的概率海啸风险.通过对历史地震数据的分析,综合考虑震级、震中位置、震源深度的随机性,形成了百万数量级的潜在地震情景集,并通过叠加近似方法实现了大量地震情景引发...