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2026 Vol.36, Issue 2 Preview Page

Research Article

Removing the Groundwater Level Effect from Borehole Strainmeter Data

시추공 변형률계 자료에서 지하수위 유발 효과 제거 방법

Minjoo Yeo1
,
Jinseong Moon1
,
Chandong Chang2*
,
Hansol Kim3
여 민주1
,
문 진성1
,
장 찬동2*
,
김 한솔3
1Undergraduate Student, Department of Geological Sciences, Chungnam National University
2Professor, Department of Geological Sciences, Chungnam National University
3Manager, Structure & Site Monitoring Team, Korea Radioactive Waste Agency
1충남대학교 지질환경과학과 학부생
2충남대학교 지질환경과학과 교수
3한국원자력환경공단 구조부지팀 과장
*Corresponding Author
30 June 2026. pp. 291-301
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Abstract

Borehole strainmeters are useful for monitoring long-term crustal deformation because they continuously record small subsurface deformation at high resolution. However, strainmeter records may contain non-tectonic components caused by environmental factors, increasing uncertainty in their interpretation. In this study, we investigate the effects of groundwater-level changes on borehole strainmeter data from a site in southeastern Korea and propose an empirical correction to remove groundwater-induced strain components. Analysis of rainfall, groundwater level, areal strain, and two shear-strain components from 2021 to 2023 shows that groundwater levels generally increased following rainfall. The daily change in groundwater level exhibits the strongest response within ~1 day after rainfall, indicating that the major short-term fluctuations in groundwater level during the study period were primarily associated with rainfall recharge. For 14 events characterized by rapid groundwater-level rises, changes in the areal and shear strains show approximately linear relationships with groundwater-level change. These relationships are used to derive empirical correction coefficients for groundwater-induced strain. Applying the correction substantially reduces repetitive short-term strain variations associated with groundwater-level fluctuations and makes long-term trends in the strain records clearer to identify. The results demonstrate that a site-specific groundwater-level correction can improve the interpretability of borehole strainmeter records. However, the tectonic significance of the residual long-period variations requires further evaluation using independent observations.

Keywords
borehole strainmeter
groundwater level
pore pressure
crustal deformation

시추공 변형률계는 지각 내 미세 변형을 고해상도로 연속 관측할 수 있어 장기 지각 변형 해석에 유용하다. 그러나 실제 관측 자료에는 지구조적 변형 신호 외에도 다양한 환경 요인에 의한 비지구조적 성분이 포함될 수 있어 자료 해석의 불확실성을 증가시킨다. 본 연구에서는 지하수위 변화가 시추공 변형률계 자료에 미치는 영향을 분석하고, 지하수위 유발 성분을 제거하기 위한 경험적 보정 방법을 제시하였다. 2021년부터 2023년까지의 강수량, 지하수위, 면적변형률 및 전단변형률 자료를 분석한 결과, 연구 지역의 지하수위는 강수 이후 뚜렷하게 상승하며, 특히 일별 지하수위 변화량은 강수 발생 후 약 1일 이내에 가장 큰 반응을 보였다. 이는 지하수위 변동의 주요 원인이 강수의 지하 침투와 이에 따른 공극압 증가임을 지시한다. 지하수위가 급격히 상승하는 구간을 대상으로 수위 변화량과 변형률 변화량 사이의 관계를 분석한 결과, 면적변형률과 두 전단변형률 모두 지하수위 변화와 선형적인 상관성을 보였으며, 이를 바탕으로 지하수위 유발 변형률 보정식을 도출하였다. 보정 후 자료에서는 지하수위 변동에 따른 반복적인 단기 변형 성분이 크게 감소하였고, 전처리 자료에서 불명확했던 장기 변형 추세가 뚜렷하게 나타났다. 보정 결과는 지하수위 보정이 시추공 변형률계 자료의 신호 대 잡음비를 향상시키고, 장기 지각 변형 해석의 신뢰도를 높이는 데 효과적임을 보여준다.

키워드
시추공 변형률계
지하수위
공극압
지각 변형
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Information
  • Publisher :Korean Society of Engineering Geology
  • Publisher(Ko) :대한지질공학회
  • Journal Title :The Journal of Engineering Geology
  • Journal Title(Ko) :지질공학
  • Volume : 36
  • No :2
  • Pages :291-301
  • Received Date : 2026-05-13
  • Revised Date : 2026-06-16
  • Accepted Date : 2026-06-17
  • DOI :https://doi.org/10.9720/kseg.2026.2.291
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