‘지진 예보’의 꿈과 현실 : 일본의 지진 예측 연구에 관한 역사적 고찰

김범성 서울대학교 일본연구소 2012 일본비평 Vol.- No.7

이 글에서는, 역사적인 관점에서 일본의 지진 예측 연구에 대해 살펴본다. 지진의 발생 을 예측하여 이로 인한 피해를 줄이고자 하는 것은 일본 지진학의 여명기부터 존재한 희망이었으나 이를 실현하는 것은 쉽지 않은 일이었고, 오히려 이로 인해 사회적인 문 제가 발생하기도 하였다. 한편 1923년의 관동대지진을 계기로 물리학자들을 중심으 로 지진 연구가 재편되는 과정에서 지진 예측보다는 기초 연구가 중시되게 되었다. 그 러나 지진 예측에 대한 열망이 사라진 것은 아니었고, 지진학자들이 1962년에 발행한 보고서를 바탕으로 1965년도부터는 지진 예측이 국가적인 사업으로 추진되기 시작하 였으며, 1978년에는 이와 관련한 법률도 제정되었다. 한편 일부 과학자들은 일찍부터 지진 예측에 대해 과학적인 근거가 박약하다고 비판을 거듭해 왔고, 결국 1995년의 고 베 지진이 계기가 되어 30년간 전개되어 온 사업에 대한 재검토가 이루어졌다. 그러나 현재에도 일본사회에는 지진의 발생을 조금이라도 빨리 포착하고자 하는 희망이 남아 있으며, 시민의 생활과 밀접한 관련을 지닌 지진 예측의 문제는 과학과 사회, 정치가 얽혀 있는 영역을 가로지르고 있다. This paper takes a historical approach in its review of the scientific quest for earthquake prediction in Japan, and the socio-political terrains where these investigations were deployed. When seismology was established in Japan in the late 19th century, the problem of earthquake prediction interested some forerunners of the newborn science. However, as seismicity is located underground, investigations proved difficult and predictions could sometimes cause social panic. In the aftermath of the Great Kanto Earthquake of 1923, a methodological turn to geophysics led Japanese scientists to make basic rather than practical investigations. It was in the 1960s that the desire for prediction was revisited, promoting a new national project crossing boundaries between scientific and socio-political realms. While criticisms of the “inability” to realize the goal have continued, Kobe’s tragedy of 1995 stimulated critics of this branch of science to emphasize basic research, similar to what their predecessors had argued seven decades ago. Thus, the history of earthquake prediction in Japan elucidates how scientific and socio-political cultures have interacted on the subject of natural disasters and their mitigation.

Upper mantle shear wave velocity structure beneath northern Victoria Land, Antarctica: Volcanism and uplift in the northern Transantarctic Mountains

Graw, J.H.,Adams, A.N.,Hansen, S.E.,Wiens, D.A.,Hackworth, L.,Park, Y. North-Holland Pub. Co ; Elsevier Science Ltd 2016 Earth and planetary science letters Vol.449 No.-

The Transantarctic Mountains (TAMs) are the largest non-compressional mountain range on Earth, and while a variety of uplift mechanisms have been proposed, the origin of the TAMs is still a matter of great debate. Most previous seismic investigations of the TAMs have focused on a central portion of the mountain range, near Ross Island, providing little along-strike constraint on the upper mantle structure, which is needed to better assess competing uplift models. Using data recorded by the recently deployed Transantarctic Mountains Northern Network, as well as data from the Transantarctic Mountains Seismic Experiment and from five stations operated by the Korea Polar Research Institute, we investigate the upper mantle structure beneath a previously unexplored portion of the mountain range. Rayleigh wave phase velocities are calculated using a two-plane wave approximation and are inverted for shear wave velocity structure. Our model shows a low velocity zone (LVZ; ~4.24 km@?s<SUP>-1</SUP>) at ~160 km depth offshore and adjacent to Mt. Melbourne. This LVZ extends inland and vertically upwards, with more lateral coverage above ~100 km depth beneath the northern TAMs and Victoria Land. A prominent LVZ (~4.16-4.24 km@?s<SUP>-1</SUP>) also exists at ~150 km depth beneath Ross Island, which agrees with previous results in the TAMs near the McMurdo Dry Valleys, and relatively slow velocities (~4.24-4.32 km@?s<SUP>-1</SUP>) along the Terror Rift connect the low velocity anomalies. We propose that the LVZs reflect rift-related decompression melting and provide thermally buoyant support for the TAMs uplift, consistent with proposed flexural models. We also suggest that heating, and hence uplift, along the mountain front is not uniform and that the shallower LVZ beneath northern Victoria Land provides greater thermal support, leading to higher bedrock topography in the northern TAMs. Young (0-15 Ma) volcanic rocks associated with the Hallett and the Erebus Volcanic Provinces are situated directly above the imaged LVZs, suggesting that these anomalies are also the source of Cenozoic volcanic rocks throughout the study area.

Characteristics in hypocenters of microseismic events due to hydraulic fracturing and natural faults: a case study in the Horn River Basin, Canada

우정웅,김주환,이준기,강태섭 한국지질과학협의회 2017 Geosciences Journal Vol.21 No.5

For two to three decades, microseismic monitoring has been popular in the development of unconventional resources, because the fracture network generated by hydraulic fracturing mainly controls the productivity, and microseismic monitoring enables direct measurements for imaging the fracture network. Nevertheless, some refinements are required to make this method more practical. One challenge is to quantify the effects of pre-existing natural fractures for generating microseismic events. We determine the hypocenters of microseismic events occurring in a shale gas play in the Horn River Basin, Canada, and report several interesting spatial and temporal features of the hypocenter distributions. Automatic phase-picking is applied to waveform data recorded at 98 shallow buried three-component geophones, and phases thought to be from the same event are associated. The initial hypocenters of events are determined by iterative linear inversion algorithm then relocated using a double-difference algorithm, where relative travel time measurements are obtained with the waveform cross-correlation. We group events into many clusters based on fracking stages and their hypocenters, and then define the best-fitting plane of hypocenters for each cluster. Most strikes of the best-fitting planes are consistent with the direction of local horizontal stress maximum, indicating that hydraulic fracturing induces most microseismic events. However, the best-fitting planes of several clusters have strikes similar to those of pre-existing faults or fractures, indicating that pre-existing natural faults or fractures can affect the generation of microseismic events. In addition, some observations suggest that natural fractures can affect the temporal evolution of the spatial occurrence pattern of microseismic events. We observed specific migration patterns of microseismic events around known faults in the study area. Although further work is required for complete understanding of this phenomenon, our observations help elucidate the nature of microseismic generation.

음향메타물질을 이용한 지진파 제어기술

김상훈 한국물리학회 2013 새물리 Vol.63 No.9

Recently, two methods of earthquake engineering using acoustic metamaterials have been suggested. One is the traditional cloaking method in which seismic waves are deflected from buildings to be protected. The other is the shadow zone method which creates an area through which seismic waves cannot pass. A fundamental difference of metamaterial methods from conventional earthquake-engineering methods is that these former methods are applied not to the buildings to be protected themselves but to the ground below the surface near the buildings to be protected. The structure to be protected does not have to be altered. We explain the fundamental principles of the two methods and compare their advantages and disadvantages. Furthermore, we introduce recent improvements in the methods. 최근 음향메타물질 분야의 발달은 음향파의 일종인 지진파를 제어하여내진설계에까지 적용하려는 움직임이 나타나고 있는데 크게 두 가지방법이 제시되었다. 하나는 전형적인 클로킹 방법으로 지진파가 건물을비껴가게 하는 것이고, 다른 하나는 인공 지진파 암영대 방법으로지진파가 통과하지 않는 인공 지진파 암영대를 조성하여 그 위의건물들을 보호하는 방법이다. 이 방법들은 건물 자체에 내진설계를 하는것이 아니라 건물 주변의 지하에 내진설계를 한다. 따라서 보호하고자하는 건물의 내진규모를 증가시키기 위하여 기존의 건물을 변경하거나 할필요가 없다. 그 외에 이 두 가지 방법의 기본 이론 및 장단점을살펴보고 및 최근의 연구내용을 소개한다.

Waveform inversion in the Laplace–Fourier domain

Shin, Changsoo,Ho Cha, Young Blackwell Publishing Ltd 2009 Geophysical journal international Vol.177 No.3

<P>SUMMARY</P><P>Since the pioneering work of Tarantola, waveform inversion has emerged as a tool for estimating velocity models of the subsurface using pre-stack seismic data. The waveform inversions have usually been performed in the time or frequency domain, but this can make it difficult to recover long-wavelength components of the velocity model due to the high non-linearity of the objective function and the lack of low-frequency components in the field data. Instead, it has been recently suggested that Laplace-domain waveform inversion can circumvent these limitations. By using the zero-frequency component of the damped wavefield, the Laplace-domain waveform inversion can recover long-wavelength structures of the velocity model even if low-frequency components less than 5 Hz are unreliable or would be unusable in conventional inversions. The main drawback is that the penetration depth of the Laplace-domain inversion depends on the offset distance and the choice of Laplace damping constants.</P><P>In this paper, we propose an improved Laplace–Fourier-domain waveform inversion to compensate for these weak points. This is accomplished by exploiting low frequency components (less than 5 Hz) of the damped wavefield. The success of this technique arises from the ‘mirage-like’ resurrection of low-frequency components less than 5 Hz and the unique characteristics of the complex logarithmic wavefield. The latter is capable of separating the wavefield into amplitude and phase components, allowing us to simultaneously generate both long-wavelength and medium-short-wavelength velocity models.</P><P>We successfully applied the Laplace–Fourier-domain waveform inversion to a synthetic data set of the BP model calculated using the time-domain finite difference method. This not only produced a more refined velocity model when compared to Laplace-domain inversion results, but it also improved the penetration depth of the inversion. Furthermore, when the velocity model produced by the Laplace–Fourier-domain waveform inversion was then used as an initial velocity model of a conventional frequency-domain inversion, we obtained an inverted velocity model containing almost every feature of the true BP model.</P><P>We applied our two-step, Laplace-domain waveform inversion to field data and obtained a refined velocity model containing short- and long-wavelength components. To convince ourselves of the accuracy of the inversion results, we computed a synthetic model using the estimated source wavelet and our velocity model from the inversion, and we obtained a migrated image and angle-domain common-image gathers at several points by a reverse-time pre-stack depth migration in the frequency domain. The reconstructed synthetic data were in good agreement with the field data and most parts of the reflections in the image gathers were flattened.</P>

Frequency-domain elastic full waveform inversion for VTI media

Lee, Ho-Yong,Koo, June Mo,Min, Dong-Joo,Kwon, Byung-Doo,Yoo, Hai Soo Blackwell Publishing Ltd 2010 Geophysical journal international Vol.183 No.2

<P>SUMMARY</P><P>To describe subsurface structures in anisotropic media properly, particularly in transversely isotropic media with a vertical symmetry axis (VTI), which frequently appear in sedimentary basin environments, we develop a frequency-domain elastic full waveform inversion algorithm for 2-D VTI media. The inversion algorithm is based on the cell-based finite-difference modelling method and the adjoint state of the wave equation.</P><P>Because the anisotropic inversion for VTI media deals with more elastic constants than the isotropic inversion, it is more prone to obtain local minimum solutions. For this reason, we may not succeed in properly describing the elastic constants of subsurface media if we only apply the standard inversion techniques to anisotropic waveform inversion. To compensate for the ill-posedness of the anisotropic waveform inversion, we couple elastic constants C<SUB>11</SUB> and C<SUB>33</SUB> based on Thomsen's relationship, which is also supported by the sensitivity analysis with respect to the parameters. To enhance the inversion results, we apply the frequency-selection strategy, moving from lower to higher frequencies and we carry out the inversion process over two stages. In both stages, all of the elastic constants are simultaneously optimized, as is done in the conventional waveform inversion. However, we only accept the inversion results for C<SUB>11</SUB>, C<SUB>33</SUB> and C<SUB>44</SUB> at the first stage, which will be used as the starting models for the second stage and C<SUB>13</SUB> is reinitialized as a linearly increasing model. We apply our waveform inversion algorithm to a simple 3-layered model and a part of the overthrust model. For the 3-layered model, the first inversion stage is enough to yield reasonable inversion results for all of the elastic constants. For the overthrust model, the second stage is needed to enhance the inversion results for C<SUB>13</SUB>.</P>

융·복합적 日本學으로서의 ‘歷史地震學’ - ‘災難學’에 대한 제언 -

송완범 한국일본학회 2014 日本學報 Vol.100 No.-

The popularity of Japan has recently been declining drastically in Korea, to an extent that Japan has essentially become a target of avoidance. In this context, researchers who focus on Japan as a field of study frequently express their concern, referring to “the crisis in which Japanology finds itself”. The current negative awareness of Japan among Koreans may be ascribed to resistance to Japanese Prime Minister Shinzo Abe's rightist historical consciousness and tendency towards militarism. Considering the superficial view of these phenomena by the general public, Korean-Japanese relations seem to be the worst since the normalization of diplomatic relations between the two countries in 1965. However, it appears that the so-called crisis associated with Japanology, as it is referred to by some within Japanology circles, may be readily attributed to external factors, especially those pertaining to a particular Japanologist’s own field of study. In other words, it is conjectured that the views of mainstream Korean researchers of Japanology are based on the experience they gained while studying in Japan. The author of this study, as a Japanese history major, recently paid attention to the 3.11 Great East Japan Earthquake that occurred in 2011. This study suggested the need for convergence and compound study across various disciplines. Furthermore, the critical mind expands to pose the question, “How could the key phrase, Safety and Disaster, be reconciled with Korean society?” As a result, it is presumed that the sense of blockage currently being experienced by Japanology researchers in Korea may be overcome by advocating a Study of Disasters, even though this may be considered an unfamiliar research field. 요즈음 한국에서는 일본에 대한 인기가 시들하다. 아니 시들함을 넘어서 거의 기피의 대상이라고 부를 정도이다. 그러다 보니 부쩍 일본을 연구의 필드로 삼는 사람들 사이에서조차 ‘일본학의 위기’라고 말하는 것을 자주 듣게 된다. 한국인들은 아베 신조 일본 총리의 우경화한 역사인식과 군국주의 성향에 대한 반발심으로 인해 일본에 대해 부정적 인식을 갖는다고 한다. 이러한 일반대중의 눈에 드러나는 현상만을 보면 한일관계는 1965년의 ‘한일국교정상화’ 이래 가장 나쁜 것같이 보인다. 그런데 일각에서 말하는 ‘일본학의 위기’는 너무나도 쉽게 위기의 탓을, 외부에서 특히 일본이라는 자신들의 필드에서 구하고 있는 것 같다. 이는 본인을 포함해 현재 한국에서의 일본학에 종사하는 연구자의 큰 흐름이 일본에서 유학한 강고한 경험에 기초하고 있기 때문일 것이다. 최근 본인은 일본역사 전공자이면서 2011년에 발생한 ‘3.11 동일본대지진’에 주목하고 있다. 이 작업을 통해 여러 학문 분야의 융·복합적 고찰이 절대적으로 필요하다는 인식을 얻기에 이르렀다. 더 나아가 ‘안전과 재난’이라는 키워드를 한국사회와 어떻게 접목시킬 것인가로 문제의식이 확장되고 있다. 그 결과, 최근에는 ‘災難學’이라는 다소 생소한 분야의 연구의 제창을 통해, 현재 한국에서의 일본학이 안고 있는 폐색감의 극복을 위한 활로 모색이 가능하지 않을까 생각한다.

지진가속도 계측 및 지진관측소 구축 타당성 연구

한상목,우남섭,하지호,김태우,이왕도,김기석,양재열,김영주 한국산업융합학회 2020 한국산업융합학회 논문집 Vol.23 No.3

Therefore, it was agreed that an earthquake monitoring station should be set up within the site of Handong University by analyzing drilling data and Disaster such as earthquakes is urgently needed to prepare for earthquakes in that people’s lives and national development depend on the nation’s ability to manage disasters. Many experts say that the Korean Peninsula is also under the influence of earthquakes and is not a safe zone for earthquakes. A seismological observatory will be established in Pohang to monitor ground sensors and study seismic characteristics through the task of “Development of Smart Sensor-based Intelligent Information Platform in Earthquake Region.” Therefore, it was agreed to set up a seismological observatory within the site of Handong University by analyzing drilling data and conducting on-site surveys in northern Pohang, which were heavily damaged by liquefaction and earthquakes. In this study, it was decided to make a comprehensive judgment by considering the geological characteristics of the site, whether it can perform functions, and the convenience of construction and maintenance for the final site of the seismological observatory discussed with Handong University. After completing a feasibility review on selecting a site for Handong University, we will establish a seismological observatory and actively utilize it for seismic research using data from alarm issuance and seismic data in the event of a future earthquake.

존 밀른(John Milne)과 지진 연구 네트워크

김범성 ( Boum Soung Kim ) 한국과학사학회 2013 한국과학사학회지 Vol.35 No.1

Focusing on the academic and the social life of the British scientist John Milne (1850-1913), this paper sketches how his research network was formed and transformed, crossing British and Japanese boundaries. Trained as a field scientist, Milne had explored the geological and geographical frontiers by the time that the Meiji government invited him to be a professor of geology and mining at the Imperial College of Engineering. Subsequently, in the Asiatic field, the scientist from the British Empire found interests in earthquakes and volcanoes as well as archaeological and anthropological topics. Mobilizing European knowledge and Japanese resources, Milne built a seismological research network in Japan and eventually expanded it to Britain. However, his research network was not immortal; even though he married a Japanese woman and attained honors from the Japanese emperor, during the age of Japan`s nationalist turn in the last decade of the nineteenth century, he left Japan. In the United Kingdom, he found that the research network available to him was insufficient. Simultaneously, the research system embedded in Japan had been appropriated by a younger generation of Japanese scientists, and its foreign origin has gradually been forgotten.

Inelastic Analysis and Damage Assessment of Hydraulic Arched Tunnels in Different Near-Fault Regions

Benbo Sun,Mingjiang Deng,Sherong Zhang,Chao Wang,Wei Cui,Xiaohua Zhao,Lei Kou,Binghan Xue 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.9

The seismic natural hazard event is a threat of unpredictable events, which can easily cause incalculable damage to hydraulic tunnels. Traditionally, it is necessary to introduce as-recorded ground motions (GMs) appropriately for hydraulic arched tunnels during seismic design to avoid the unfavorable situation of large-scale collapse. However, the lack of adequate current selected methodology considering the accurate engineering site relative to the fault line in this type can result in more considerable deformations and severe damage to structures. Actually, the detailed explanation of the seismic design code of hydraulic tunnels cannot support the specific consideration of the spatial region effects since the considerable uncertainty of engineering sites in water resources and hydropower engineering. To address this issue, the present study proposes a novel selected methodology of as-recorded GMs that integrates the geographic location distribution of the strong earthquake monitoring station instead of the actual engineering site relative to the fault line. Subsequently, three-dimensional finite element models of a hydraulic arched tunnel reveal the possible seismic behavior of the tunnel induced by as-recorded GMs in different near-fault regions. Furthermore, the optimal IM between different near-fault regions and structural responses is also discussed through correlation analysis because it can describe the seismological features of as-recorded GMs, which has a crucial role in seismic design and performance assessment. The results reveal that the as-recorded GMs in the hanging wall region can induce more significant deformations and severe damage to the structure than other near-fault regions of as-recorded GMs. Meanwhile, the seismological characteristics and selected optimal IM for as-recorded GMs in different near-fault regions significantly differ. In summary, data and observations from these results highlight that considering the near-fault region effect is critical in optimizing the seismic design code.