美国地震学会通报(BSSA)2008年四川汶川地震专集介绍

四川汶川MW7．9地震发生在2008年5月12日北京时间14时28分（国际协调时问6时28分）。地震的突然来袭令人措手不及,因为这个位于青藏高原边缘的地区并没有被列为地震高危险区。地震造成了巨大破坏：400多万居民无家可归,伤亡人数超过8万,并有重大的经济损失。这次地震是中国近几个世纪以来最大的地震灾难之一,     

Non-linear filter, using the wavelet transform, applied to seismological records

As any process in Nature, seismic recordsare affected by noise that the analystwould want to eliminate. One of the mostcommon techniques used to minimise thisnoise effect is the application of linearfilters, which reduce the bandwidth of thesignal. This method is based on the FourierTransform, and therefore any perturbationon the coefficients affects the entirerecord.We have developed a non-linear filter basedon the multiresolution analysis of theDiscrete Time Wavelet Transform (DTWT). Themain idea is to use the time-frequencylocalisation properties of the waveletdecomposition. Each coefficient isassociated to a window on thetime-frequency plane, so any perturbationwould only affect the time and frequencyrange of the correspondent window.The procedure we propose has three stages:periodic noise elimination, spikesreduction and, finally, the non-linearfiltering. The non-linear filter acts bythresholding the wavelet coefficients. Thethresholding estimator will depend on thesignal-noise ratio (SNR) in each of thefrequency bands associated to the waveletdecomposition.We have compared the proposed method to thecoherent structures method (Mallat, 1998)and to two 4^th order linear filterbanks (Butterworth and Elliptic filters),applying all of them to a syntheticdatabase, and a real earthquake databaserecorded by the Short Period ROA Network.The proposed method improves the SNR in the87% of the tested events, being therelative rms error less than three, and themaximum amplitude relative error less than10% in the 90% of the synthetic database.     

Compressibility of the calcium aluminosilicate, CAS, phase to 44 GPa

In situ X-ray diffraction measurements on a calcium aluminosilicate (CAS) phase have been carried out using a laser-heated diamond anvil cell up to a pressure of 44 GPa, employing a synchrotron radiation source. CAS is the major mineral formed from sediments subducted into the Earth's mantle. The sample was heated using a YAG laser after each pressure increment to relax the deviatoric stress in the sample. X-ray diffraction measurements were carried out at T = 300 K using an angle-dispersive technique. The pressure was calculated using an internal platinum metal pressure calibrant. The Birch–Murnaghan equation of state for the CAS phase obtained from the experimental unit cell parameters showed a density of ρ₀ = 3.888 g/cm³ and a bulk modulus of K₀ = 229 ± 9 GPa for K^′₀ = 4.7 ± 0.7. When the first pressure derivative of the bulk modulus was fixed at K^′₀ = 4, then the value of K₀ = 239 ± 2 GPa. From the experimental compressibility, the density of the CAS phase was observed to be lower than the density of co-existing Al-bearing stishovite, calcium perovskite, calcium ferrite-type phases, and (Fe,Al)-bearing Mg-perovskite in subducted sediments in the lower mantle. Therefore, the density of subducted sediments in the lower mantle decreases with increasing mineral proportion of the CAS phase.     

Ionospheric response to the partial solar eclipse of March 29, 2006, according to the observations at Nizhni Novgorod and Murmansk

The results of observations of the solar eclipse ionospheric effects on March 29, 2006, are presented. The observations were conducted using the partial reflection method near Nizhni Novgorod and the vertical sounding method at the automatic ionospheric station near Murmansk. It has been obtained that the electron density at altitudes of 77 and 91 km decreases by a factor of more than 4; in this case the response of the ionosphere at an altitude of 91 km lags behind the eclipse maximum phase on the Earth by approximately 20 min. It has been established that the eclipse in the E and F1 regions of the polar ionosphere causes a change in the electron density by 15–20%. The delay time of this effect varies from 12 to 24 min depending on the altitude. It has been registered that the reflection virtual altitude at altitudes of the ionospheric F region increases in Murmansk and Nizhni Novgorod.     

Analytical approximation to the solutions of Richards' equation with applications to infiltration,ponding, and time compression approximation

A recent approach to solve Richards' equation is further improved. This approach brings understanding into the physical processes of infiltration and ponding. In particular we apply it to analyze the standard hydrologic tool of Time Compression Approximation (TCA). We also suggest that the new approach provides a more reliable alternative to TCA, e.g. for predicting ponding time.     

Welcoming a monster to the world: Myths,oral tradition,and modern societal response to volcanic disasters

Volcanic eruptions can overwhelm all senses of observers in their violence, spectacle and sheer incredibility. When an eruption is catastrophic or unexpected, neither individuals nor communities can easily assimilate the event into their world view. Psychological studies of disaster aftermaths have shown that trauma can shake the very foundations of a person's faith and trigger a search – supernatural, religious, or scientific – for answers. For this reason, the ability to rapidly comprehend a traumatic event by “accepting” the catastrophe as part the observer's world represents an important component of community resilience to natural hazards. A relationship with the event may be constructed by adapting existing cosmological, ancestral, or scientific frameworks, as well as through creative and artistic expression. In non-literate societies, communal perceptions of an event may be transformed into stories that offer myth-like explanations. As these stories make their way into oral traditions, they often undergo major changes to allow transmission through generations and, in some cases, to serve political or religious purposes. Disaster responses in literate societies are no different, except that they are more easily recorded and therefore are less prone to change over time.     

Numerical analogs to Fourier and dispersion analysis: development,verification, and application to the shallow water equations

Herein, we present numerical analogs to traditional Fourier and dispersion analyses and validate them with well-characterized phase behavior for classic finite difference and finite element (FE) discretizations of the shallow water equations. Basically, the procedure is to introduce a single wave with known amplitude and phase into the domain, propagate the wave approximately one wavelength using some discretization scheme, and then note its final amplitude and phase. The final state of the wave is then compared with the expected wave form predicted by the continuum equations to determine the propagation behavior of the discretization. After validating the technique, we then examine two case studies: (1) slope limiting schemes within the finite volume framework and (2) lumping coefficients within the selective lumping FE framework. Of the three common slope limiters that we examined, the Superbee limiter has the most promising phase behavior, as it is the least dissipative while maintaining minimal phase error. Using our numerical technique, we were also able to verify the range of values that has been found to be most accurate in practice for the selective lumping coefficient.     

Simulation of the damage to a simple RC structure in the Bhuj,India, earthquake to estimate the level of input‐motion

Analysis of a simple reinforced concrete (RC) structure damaged by the Bhuj, India, earthquake was carried out to estimate the level of shaking in the epicentral region. For this, an attempt was made to estimate the level of input motion to cause inelastic behavior to the extent observed during the field visit. To consider the inelastic effects, both yielding of steel bars as well as crushing of the concrete cover has been investigated employing the hysteretic model known as the Fiber model. The only available record at Ahmedabad of the Bhuj earthquake and four additional earthquake records from Japan and California were used in the analysis. Considering simple scaling of input motion, the level of input motion to cause crushing and spall‐off of the concrete cover as observed in the field was estimated to be of the order of 6 times the original instrumental record obtained at 240 km away from the epicenter. The methodology proposed was promising in providing a useful quantitative indication of the level of shaking when instrumental records are not available. It was also noted that the design response spectrum specified in Indian seismic code IS1893: 1984 appears inadequate compared to the extent of shaking estimated. Copyright © 2005 John Wiley & Sons, Ltd.     

A search for precursors to the Sitka, 1972, earthquake: Sea level,magnetic field,andP-residuals

Summary The Sitka earthquake of 30 July, 1972, was a shallow strike-slip fracture of 170 km lenght and it closed a gap defined bySykes (1971). A tide gauge station, a magnetic observatory and a seismological station are located 40 km to the east of the center of the rupture. A comparison of the sea level at Sitka with that at three tide gauges up to 430 km from Sitka indicates that the sea level at Sitka remained constant for 32 years before the earthquake (standard deviation ±1.5 cm) with the exception of the years 1966 and 1967 when the land may have been elevated by 3 cm. Preliminary analysis of mean teleseismic-P-residuals suggests that aP-wave delay may have existed under the station Sitka during 1966 and 1967. The quiet annual means of the horizontal component of the magnetic field at Sitka were compared to that at College, Alaska, and Victoria, Canada, for all years since the establishment of these stations in 1941 and 1957 respectively. Starting 7.5 years before the earthquake the field differences appear to have decreased by approximately 20, gradually returning to normal the year after the earthquake.     

Ashes to ashes, dust to dust

An account of the RAS Presidential Address of 11 February 2000, given by David A Williams , Perren Professor of Astronomy, University College London.     

The response of the Sao Paulo Continental Shelf, Brazil, to synoptic winds

The response of the Sao Paulo Continental Shelf (SPCS) to synoptic wind forcing has been analyzed. Two different methods are used for this purpose, one based on hydrographic data, bottom topography, and geographical characteristics, and a second on analyzing currentmeter data directly and using empirical orthogonal functions. Both methods show similar results for an essentially barotropic shelf. The SPCS response in the subinertial frequency band appears to be trapped on the continental shelf. Numerical experiments have also been carried out showing results that qualitatively agree with the observations, including the velocity component parallel to the coastline. Supported by CAPES.     

悼念王仁院士

我国著名的力学家、地球动力学家和力学教育家、中国科学院院士、北京大学力学与工程科学系暨地球物理系教授、中国共产党党员王仁先生因病医治无效 ,不幸于 2 0 0 1年 4月 8日 10时 48分在北京协和医院逝世 ,享年 80岁。王仁先生 192 1年 1月 2日出生于浙江省吴兴县。 1943年毕业于西南联大航空工程系并获得工学学士学位。 1944年春到贵阳飞机制造厂做设计员工作。 1945年抗战胜利后被派到台湾参加对日军修理厂的接收工作 ,在台中市第三飞机制造厂任工程师。 1948～ 195 0年在美国西雅图华盛顿大学航空工程系继续深造 ,于19 5 0年获理学硕…     

Fragmentation and assembly of the continents,Mid-carboniferous to present

Eighteen maps showing the motions of the major continents following the break-up of Wegener's Pangaea in the Early to Mid-Jurassic are presented. Palaeolatitudes are determined palaeomagnetically, palaeolongitudes mainly from sea-floor spreading evidence. The break-up commences with the opening of the southern North Atlantic in the mid-Jurassic and its extension north and south in the Cretaceous and Cenozoic. Concurrently the northern continents move northwards away from the southern continents (Gondwana) and a continuous east-west seaway is formed between them in the Cretaceous. Successive fragmentation of continents then created the Arctic, Indian and Antarctic Oceans. Five maps showing the disposition of land in the Permian are also given. These are based on the palaeomagnetic evidence and the idea of minimizing the motions required to bring the continents into their known Early Jurassic configuration. The Permian maps show Gondwana situated further east than in the Pangaea configuration of Wegener. There are severe problems in constructing palaeogeographical maps for the Triassic and none are presented. Palaeomagnetic results from smaller crustal fragments are also reviewed and the evidence for the former dismemberment of Eurasia and the western part of the North American cordillera are set out. The results indicate that most orogenies are to some degree collisional in nature.     

Contribution to the Global Warming Mitigation of Marshlands Conversion to Croplands in the Sanjiang Plain,Northeast China

Based on the estimation of greenhouse gases (GHG) emissions and carbon sequestration of the total conversion of marshlands (TMC), marshlands conversion to paddy fields (MCPFs) and marshlands conversion to uplands (MCULs), this study revealed the contribution to the global warming mitigation (CGWM) of paddy fields versus uplands converted from marshlands in the Sanjiang Plain (excluding the Muling‐Xingkai Plain on south of Wanda Mountain), Heilongjiang Province, northeast China. The results showed that the total area of MCPFs and MCULs was 504.23 × 10³ ha between 1982 and 2005. The CGWM per unit area was 45.53 t CO₂eq/ha for MCPFs and that was 23.95 t CO₂eq/ha for MCULs, with an obvious 47.40% reduction. The MCPFs and MCULs ecosystems acted as the carbon sink all of the year. As far as CGWM per unit area is concerned, MCPFs mitigated the greenhouse effect which was greater than MCULs. And it was effective that the implementation of the uplands transformed into paddy fields in Northeast China with regard to marshlands protection and croplands (including paddy fields and uplands) reclamation.     

哈萨克斯坦共和国科教部地震研究所所长来疆工作访问

应新疆地震局邀请 ,哈萨克斯坦共和国科教部地震研究所所长努西波夫、高级工程师阿不都拉耶夫、乌兹别克夫于 2 0 0 3年 7月 2 5日至 8月 1日对新疆维吾尔自治区地震局进行了为期 7天的工作访问。访问期间 ,哈专家在有关人员陪同下参观并考察了库尔勒地震台及地震观测山洞。地震观测山洞先进的地震观测仪器、理想的观测环境给哈专家留下了深刻印象。哈专家对考察结果非常满意并希望今后双方加强联系与交流 ,开展更广领域、更深层次的合作。考察结束后双方专家召开讨论会 ,就阿拉木图地震形势交换了意见。此外 ,哈专家还介绍了哈萨克斯坦共和…     

A Brief Introduction to the Wenchun Ms8.0 Earthquake Sequence, May 12, 2008

A total of 190 aftershocks with Ms≥4.0 occurred until May 31, 2008, after the earthquake with Ms8.0 on May 12, 2008, in Wenchuan, Sichuan, according to the Chinese Seismic Station Network (Table 1). Among them, there are 160 events of Ms4.0 - 4.9, 25 events of Ms5.0 - 5.9, and 5 events of Ms6.0 - 6.9. The strongest aftershock is the Qingchuan earthquake with Ms6.4 on May 25. 1 Received on June 3. 2008.     

Asymmetric response of the topside ionosphere to large-scale IGW generated during the November 30, 1979, substorm

We used bottomside ground observations and topside sounding data from the Intercosmos-19 satellite to study a Travelling Ionospheric Disturbance (TID) that occurred in response to Large-Scale Internal Gravity Wave (LSIGW) propagation during a substorm on November 30, 1979. We built a global scheme for the wavelike ionospheric variations during this medium substorm (AE_max ～800 nT). The area where the TID was observed looks like a wedge since it covers the nighttime hours at subauroral latitudes but contracts to a ～02 h local sector at low latitudes. The ionospheric response is strongly asymmetric because the wedge area and the TID amplitude are larger in the winter hemisphere than in the summer hemisphere. Clear evidence was obtained indicating that the more powerful TID from the Northern (winter) hemisphere propagated across the equator into the low latitude Southern (summer) hemisphere. Intercosmos-19 observations show that the disturbance covers the entire thickness of the topside ionosphere, from h_mF2 up to at least the 1000 km satellite altitude at post-midnight local times. F-layer lifting reached ～200 km, N_e increases in the topside ionosphere by up to a factor of ～1.9 and variations in N_mF2 of both signs were observed. Assumptions are made concerning the reason for the IGW effect at high altitudes in the topside ionosphere. The relationship between TID parameters and source characteristics determined from a global network of magnetometers are studied. The role of the dayside cusp in the generation of the TID in the daytime ionosphere is discussed. The magnetospheric electric field effects are distinguished from IGW effects.     

Kinematics, structure and relationship to metamorphism of the east-west flow in the Sanbagawa Belt, southwest Japan

Abstract Deformation in the Sanbagawa Belt is characterized by ductile flow in an east-west direction sub-parallel to its length. The east-west flow (D₁) caused large-scale recumbent folding of the metamorphic sequence in central Shikoku, which can explain the inverted thermal structure of this region. Chemical zoning of metamorphic minerals associated with D₁ microstructures also suggest that the east-west flow developed under retrograde conditions. D₁ is therefore related to exhumation rather than subduction processes. A variety of kinematic indicators show that during the east-west flow, deformation was partitioned into structurally continuous domains with opposed senses of shear. This suggests that bulk deformation was not simple shear but included a component of flattening.     

Coastal blue carbon: Concept,study method,and the application to ecological restoration

Coastal blue carbon refers to the carbon taken from atmospheric CO2; fixed by advanced plants(including salt marsh,mangrove, and seagrass), phytoplankton, macroalgae, and marine calcifiers via the interaction of plants and microbes; and stored in nearshore sediments and soils; as well as the carbon transported from the coast to the ocean and ocean floor. The carbon sequestration capacity per unit area of coastal blue carbon is far greater than that of the terrestrial carbon pool. The mechanisms and controls of the carbon sink from salt marshes, mangroves, seagrasses, the aquaculture of shellfish and macroalgae, and the microbial carbon pump need to be further studied. The methods to quantify coastal blue carbon include carbon flux measurements, carbon pool measurements, manipulative experiments, and modeling. Restoring, conserving, and enhancing blue carbon will increase carbon sinks and produce carbon credits, which could be traded on the carbon market. The need to tackle climate change and implement China's commitment to cut carbon emissions requires us to improve studies on coastal blue carbon science and policy. The knowledge learned from coastal blue carbon improves the conservation and restoration of salt marshes,mangroves, and seagrasses; enhances the function of the microbial carbon pump; and promotes sustainable aquaculture, such as ocean ranching.     

Temperature Trends and Changes in Rize,Turkey, for the Period 1975 to 2007

There is increasing evidence that the global climate is changing as a result of anthropogenic activity. Short‐term mean, maximum, and minimum temperatures of the city Rize located at the Eastern Black Sea Coast of Turkey were analyzed to reveal trends, change points, significant warming (cooling) periods, and trend rates per year. An increasing trend of approximately 1.27°C/33 years (α = 0.001) in the annual mean temperatures is found during the period from 1975 to 2007. Two periods, averaging 13.78 and 14.66°C, respectively, were detected from fluctuation in the annual mean temperatures. The trend of the first period (1975–1993) is towards a cooler climate, whereas the trend of the second period (1994–2007) is towards a warmer climate. Summer, autumn and, particularly, the spring mean temperatures have tended to increase strongly, whereas the winter mean temperatures have increased slightly over the whole period. For the winter mean temperature, the trend rate indicates a slight increase, which is insignificant. Maximum temperatures have dramatically increased with 1.61°C (α = 0.001) over the last 33 years. However, annual minimum temperatures have increased by 0.99°C (α = 0.01) over the same period.