A combination of tides and nontidal variations in ocean bottom pressure may generate interannual slip fluctuations in the transition zone along a subduction plate interface

IF 2.8 4区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Yoshiyuki Tanaka , Hiromu Sakaue , Masayuki Kano , Suguru Yabe
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引用次数: 3

Abstract

The tidal triggering of earthquakes has been studied for many years. The discovery of slow earthquakes in the early 2000s, including slow slip, has urged scientists to investigate the tidal responses of these earthquakes due to their sensitivity to weak stress perturbations. Previous studies have shown that slow earthquakes correlate with diurnal and semidiurnal tides and seasonal variations in surface loads more clearly than ordinary earthquakes. However, little is known about long-term responses to external stresses. In this paper, based on a widely accepted frictional law for faults, a mechanism is proposed by which nontidal variations in ocean bottom pressure, when combined with tides, promote the occurrence of slow earthquakes. Because slow earthquakes accompany a slip on the plate interface, this mechanism allows one to estimate slip modulations. A one-degree-of-freedom slip model is constructed and applied to Ise Bay in the Tonankai region of southwestern Japan, where large-scale ocean mass redistributions have occurred. The model calculated with parameters determined from the observation of tectonic tremors is quantitatively consistent with the slip during 1997–2013 inferred from GNSS data, suggesting that the decrease in the sea-level change in approximately 2006 could cause the acceleration of a slip observed after that. This result implies that the decreases in sea level in approximately 1996 and 2014 could also cause subsequent slip accelerations. These three slip acceleration periods temporally coincide with the increases in background seismicity in a shallower portion of the plate interface. These changes in seismicity are common to shallow earthquakes in the Tokai area, and a similar model can reproduce them. Further studies are expected to reveal causality between shallow earthquakes and long-term slip fluctuations based on modeling that considers changes in the frictional property along the plate interface.

潮汐和海底压力的非潮汐变化可能会在俯冲板块界面的过渡带产生年际滑动波动
地震的潮汐触发已经被研究了很多年。21世纪初发现的缓慢地震,包括缓慢滑动,促使科学家研究这些地震的潮汐反应,因为它们对弱应力扰动很敏感。以前的研究表明,慢震与日、半日潮汐和地表负荷的季节变化的关系比普通地震更明显。然而,人们对外界压力的长期反应知之甚少。本文基于一个被广泛接受的断层摩擦规律,提出了海底压力的非潮汐变化与潮汐结合时促进慢震发生的机制。因为缓慢的地震伴随着板块界面的滑动,这种机制允许人们估计滑动调制。建立了一自由度滑动模型,并将其应用于日本西南部东海地区伊势湾,该地区发生了大规模的海洋质量再分布。根据构造地震观测确定的参数计算的模型与GNSS数据推断的1997-2013年的滑动在数量上是一致的,这表明2006年前后海平面变化的减小可能导致此后观测到的滑动加速。这一结果表明,大约1996年和2014年的海平面下降也可能导致随后的滑动加速。这三个滑动加速期在时间上与板块界面较浅部分背景地震活动性的增加相吻合。这些地震活动性的变化在东海地区的浅层地震中很常见,一个类似的模型可以再现它们。进一步的研究预计将揭示浅层地震和长期滑动波动之间的因果关系,基于考虑沿板块界面摩擦特性变化的建模。
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来源期刊
Geodesy and Geodynamics
Geodesy and Geodynamics GEOCHEMISTRY & GEOPHYSICS-
CiteScore
4.40
自引率
4.20%
发文量
566
审稿时长
69 days
期刊介绍: Geodesy and Geodynamics launched in October, 2010, and is a bimonthly publication. It is sponsored jointly by Institute of Seismology, China Earthquake Administration, Science Press, and another six agencies. It is an international journal with a Chinese heart. Geodesy and Geodynamics is committed to the publication of quality scientific papers in English in the fields of geodesy and geodynamics from authors around the world. Its aim is to promote a combination between Geodesy and Geodynamics, deepen the application of Geodesy in the field of Geoscience and quicken worldwide fellows'' understanding on scientific research activity in China. It mainly publishes newest research achievements in the field of Geodesy, Geodynamics, Science of Disaster and so on. Aims and Scope: new theories and methods of geodesy; new results of monitoring and studying crustal movement and deformation by using geodetic theories and methods; new ways and achievements in earthquake-prediction investigation by using geodetic theories and methods; new results of crustal movement and deformation studies by using other geologic, hydrological, and geophysical theories and methods; new results of satellite gravity measurements; new development and results of space-to-ground observation technology.
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