• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2005년도 공동학술대회 논문집
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• pp.93-101
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• 2005

본 연구에서는 지진 예지 연구를 위하여 한반도에서 발생한 MMI 진도가 VIII 보다 큰 역사 지진들의 전진들에 대하여 지진활동도의 변화를 분석하였다. 한반도에서의 강진에 대하여 13년의 전진기간과 진앙을 중심으로 위도 $1.1^{\circ}$, 경도 $1.1^{\circ}$ 크기의 사각형 모양의 전진범위를 가정했을 경우 가장 안정적인 전진들의 b값을 도출할 수 있었다. 이 전진기간과 전진범위에 의해 결정된 11개의 MMI 진도 VIII 이상의 강진의 전체 전진들에 대한 b값은 전체 역사지진의 b값인 0.36에 비해 확연히 작은 0.27로 결정되었다. 또한 강진 발생을 앞두고 작은 b값을 가지는 지진들이 강진의 진앙 근처에서 집중적으로 발생하였다. 본 연구를 통해 십 수 년 동안의 b값의 변화를 자세히 관찰함으로써 강진의 예지가 가능하다는 것이 확인되었다.

• 지구물리
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• 제8권3호
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• pp.115-121
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• 2005

본 연구에서는 지진 예지 연구를 위하여 한반도에서 발생한 MMI 진도가 VIII 보다 큰 역사 지진들의 전진들에 대하여 지진활동도의 변화를 분석하였다. 한반도에서의 강진에 대하여 13년의 전진기간과 진앙을 중심으로 위도 1.1o, 경도 1.1o 크기의 사각형 모양의 전진범위를 가정했을 경우 가장 안정적인 전진들의 b값을 도출할 수 있었다. 이 전진기간과 전진범위에 의해 결정된 11개의 MMI 진도 VIII 이상의 강진의 전체 전진들에 대한 b값은 전체 역사지진의 b값인 0.36에 비해 확연히 작은 0.27로 결정되었다. 또한 강진 발생을 앞두고 작은 b값을 가지는 지진들이 강진의 진앙 근처에서 집중적으로 발생하였다. 본 연구를 통해 십 수 년 동안의 b값의 변화를 자세히 관찰함으로써 강진의 예지가 가능하다는 것이 확인되었다.

• Geomechanics and Engineering
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• 제38권6호
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• pp.621-631
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• 2024

In designing earthquake-resistant structures, we traditionally select dynamic loads based on the recurrence period of earthquakes, using individual seismic records or aligning them with the design spectrum. However, these records often represent isolated waveforms lacking continuity, underscoring the need for a deeper understanding of natural seismic phenomena. The Earth's crustal movement, both before and after a significant earthquake, can trigger a series of both minor and major seismic events. These minor earthquakes, which often occur in short time before or after the major seismic events, prompt a critical reassessment of their potential impact on structural design. In this study, we conducted a detailed tunnel response analysis to assess the impact of both single mainshock and multiple earthquake scenarios (including foreshock-mainshock and mainshock-aftershock sequences). Utilizing numerical analysis, we explored how multiple earthquakes affect tunnel deformation. Our findings reveal that sequential seismic events, even those of moderate magnitude, can exert considerable stress on tunnel lining, resulting in heightened bending stress and permanent displacement. This research highlights a significant insight: current seismic design methodologies, which predominantly focus on the largest seismic intensity, may fail to account for the cumulative impact of smaller, yet frequent, seismic events like foreshocks and aftershocks. Our results demonstrate that dynamic analyses considering only a single mainshock are likely to underestimate the potential damage (i.e., ovaling deformation, failure lining, permanent displacement etc.) when compared to analyses that incorporate multiple earthquake scenarios.

• Earthquakes and Structures
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• 제8권1호
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• pp.153-184
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• 2015

Most damaging earthquakes come as complex sequences characterized by strong aftershocks, sometimes by foreshocks and often by multiple mainshocks. Complex earthquake sequences have enormous seismic hazard, engineering and societal implications as their impact on buildings and infrastructures may be much more severe at the end of the sequence than just after the mainshock. In this paper we examine whether historical sources can help characterizing the rare earthquake sequences of pre-instrumental times in full, including fore-, main- and aftershocks. Thanks to the its huge documentary heritage, Italy relies on one of the richest parametric earthquake catalogues worldwide. Unfortunately most current methods for assessing seismic hazard require that earthquake catalogues be declustered by removing all shocks that bear some dependency with those identified as mainshocks. We maintain that this requirement has led most modern historical seismologists to focus mainly on mainshocks rather than also on the fore- and aftershocks. To shed light onto major earthquake sequences of the past, rather than onto individual mainshocks, we investigated 10 damaging earthquake sequences ($M_w$ 4.7-7.0) that hit the L'Aquila area and central Abruzzo from the 14th to the 20th century. We find that most of the results of historical research are important for modern seismology, yet their rendering by the current parametric catalogues causes most information to be lost or not easily transferred to the potential users. For this reason we advocate a change in current strategies and the creation of a more flexible standard for storing and using all the information made available by historical seismology.

• Structural Engineering and Mechanics
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• 제32권4호
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• pp.563-581
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• 2009

In this paper, the peak horizontal ground acceleration over the bedrock (PGA) is calculated by a probabilistic seismic hazard assessment (PSHA). For this reason, at first, all the occurred earthquakes in a radius of 200 km of Sanandaj city have been gathered. After elimination of the aftershocks and foreshocks, the main earthquakes were taken into consideration to calculate the seismic parameters (SP) by Kijko (2000) method. The seismotectonic model of the considered region and the seismic sources of the region have been modeled. In this research, Sanandaj and its vicinity has been meshed as an 8 (vertical lines) * 10 (horizontal lines) and the PGA is calculated for each point of the mesh using the logic tree method and the five attenuation relationships (AR) with different weighted coefficient. These calculations have been performed by the Poisson distribution of four hazard levels. Then by using it, four regional maps of the seismic hazard regions have been provided for Sanandaj and its vicinity. The results show that the maximum and minimum value of PGA for the return periods of 75, 225, 475, 2475 years are (0.114, 0.074) (0.157, 0.101), (0.189, 0.121) and (0.266, 0.170), respectively.

• Earthquakes and Structures
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• 제18권2호
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• pp.147-162
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• 2020

This paper presents a novel precast energy dissipation shear wall (PEDSW) structure system that using mild steel dampers as dry connectors at the vertical joints to connect adjacent wall panels. Analytical studies are systematically conducted to investigate the seismic performance of the proposed PEDSW under sequence-type ground motions. During earthquake events, earthquake sequences have the potential to cause severe damage to structures and threaten life safety. To date, the damage probability of engineering structures under earthquake sequence has not been included in structural design codes. In this study, numerical simulations on single-story PEDSW are carried out to validate the feasibility and reliability of using mild steel dampers to connect the precast shear walls. The seismic responses of the PEDSW and cast-in-place shear wall (CIPSW) are comparatively studied based on nonlinear time-history analyses, and the effectiveness of the proposed high-rise PEDSW is demonstrated. Next, the foreshock-mainshock-aftershock type earthquake sequences are constructed, and the seismic response and fragility curves of the PEDSW under single mainshock and earthquake sequences are analyzed and compared. Finally, the fragility analysis of PEDSW structure under earthquake sequences is performed. The influences of scaling factor of the aftershocks (foreshocks) to the mainshocks on the fragility of the PEDSW structure under different damage states are investigated. The numerical results reveal that neglecting the effect of earthquake sequence can lead to underestimated seismic responses and fragilities, which may result in unsafe design schemes of PEDSW structures.

• 대한원격탐사학회지
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• 제34권6_4호
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• pp.1489-1501
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• 2018

2016년 일본 구마모토 현에서는 규모 6.5, 6.4의 전진과 7.3의 본진, 그리고 2,000회 이상의 여진이 연속적으로 발생하였다. 이 지진에 의하여 큰 지표변위가 발생하였으며, 지진에 의하여 발생한 단층의 구조에 관한 연구를 위하여 3차원 지표변위 관측치가 제시된 바 있다(Baek, 2017). 그 관측치는 ALOS PALSAR-2 두 쌍의 상향궤도 위성레이더 간섭쌍(20160211_20160602, 20151119_20160616)과 한 쌍의 하향궤도 위성레이더 간섭쌍(20160307_20160418)을 활용하였다. 특히 상향궤도 간섭쌍의 다중개구간섭영상에서 존재하는 이온층 효과에 의하여 여진에 의한 지표변위가 포함되지 않은 하향궤도 다중개구간섭영상만을 활용하였다. 이 때문에 남북방향의 변위를 추출하는 데에 약 2달의 시간적 불일치가 존재하였다. 본 연구에서는 이러한 불일치를 저감하고 보다 정확한 단층 거동을 파악하기 위하여 상향궤도 다중개구간섭영상에 대하여 방향필터 기반 이온층 오차 저감 기법을 적용하였다. 이온층 보정 결과 여진에 의한 지표변위로 판단되는 변위 신호가 추가적으로 관측되었다. GPS 상시관측소의 지표변위 관측결과와 비교하였을 때 이온층 보정이후 9.87, 8.13 cm의 관측정밀도를 나타냈다. 이는 두 간섭쌍에 대하여 각각 기존 결과보다 4.8배, 6.4배 향상된 결과이다. 이와 같은 관측 결과는 2016 구마모토 지진을 야기한 단층의 보다 정확한 거동을 제시하는 데에 활용될 것이다.