Systematic Investigation of Dynamic Earthquake Triggering in Japan

Mapping Intimacies ◽

10.5194/egusphere-egu21-2548 ◽

2021 ◽

Author(s):

Bogdan Enescu ◽

Yuki Takeda

Keyword(s):

Systematic Investigation ◽

Earthquake Triggering ◽

Significance Level ◽

Dynamic Triggering ◽

Stress Triggering ◽

Remote Triggering ◽

Pressure Changes ◽

Large Earthquakes ◽

Swarm Earthquakes ◽

Triggering Threshold

Introduction. Previous studies (e.g., Harrington and Brodsky, 2006) documented a relative scarcity of remote triggering in Japan, compared to other seismic regions. For example, in California, dynamic triggering is reported to occur at levels of stress as small as 0.1 kPa, while in Japan it was reported that levels of 30 kPa or more are required to trigger detectable events (van der Elst and Brodsky, 2010). However, the threshold dynamic triggering level following the 2016 M7.3 Kumamoto earthquake was of just a few kPa (Enescu et al., 2016). Enescu et al. (2016) proposed that one of the possibilities to explain this observation is a change of stress triggering threshold that may have taken place after the 2011 M9.0 Tohoku-Oki earthquake.Motivation. Given the above observations, this study investigates 1) the occurrence of dynamically triggered earthquakes in Japan after some large earthquakes from 2004, and 2) whether the threshold of dynamic triggering may have changed due to the 2011 Tohoku-Oki earthquake and why this threshold might have changed.Analysis and Results. First, we investigated dynamic triggering throughout Japan, following some large earthquakes occurred after 2004. As a result, the &#160;threshold appears to decrease following the 2011 Tohoku-Oki earthquake, however the number of earthquakes we have investigated was relatively small, so we could not draw statistically significant conclusions. In the second part of the study, we have focused on a few specific areas within Japan to systematically investigate dynamic triggering, which reduced significantly the computational costs. Thus, we focused on some areas in Tohoku and Hida, where swarm earthquakes occurred after the 2011 Tohoku-Oki earthquake. As a result, the change of the triggering level in an area close to the Yamagata-Fukushima border is considered to be statically significant at a 5% significance level. In other regions, the significance at a 5% level could not be established, however a decrease of this threshold is apparent, except for one region. We speculate that changes in the stress triggering threshold levels might be related to pore pressure changes in the crust following the 2011 Tohoku-Oki earthquake.

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Absence of Near-Trench Early Triggering during the 2012 Mw 7.2 Indian Ocean Strike-Slip Earthquake: Evidence from One-Day Aftershocks

Seismological Research Letters ◽

10.1785/0220210174 ◽

2021 ◽

Author(s):

Bo Jia ◽

Han Yue ◽

Muzli Muzli

Keyword(s):

Indian Ocean ◽

Dynamic Stress ◽

Vital Role ◽

Earthquake Triggering ◽

Dynamic Triggering ◽

Earthquake Interaction ◽

Stress Triggering ◽

Completeness Magnitude ◽

Seismic Hazard Estimation ◽

Dynamic Stress Triggering

Abstract Dynamic earthquake triggering is a widely accepted mechanism of earthquake interaction, which plays a vital role in seismic hazard estimation, although its efficacy at regional distances is under debate. The 2012 Mw 7.2 Indian Ocean event is one of the first reported events to produce dynamic stress triggering at regional distances using backprojection (BP) techniques. Alternatively, the coherent radiators in BP images can be interpreted as localized water reverberation phases. We present further evidence against near-trench triggering during this event. We collected 24 hr seismic recordings of two nearby stations located near the trench. We adopted a waveform denoising algorithm and detected 125 aftershocks using two regional seismic stations with a minimum magnitude of ML∼2.7 and completeness magnitude of ML∼3.6, whereas none of these aftershocks occurred near the trench. The absence of immediate (within one day) aftershocks near the trench suggest the absence of dynamic triggering during the offshore mainshock.

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Foreshocks of the 2018 ML 4.0 Shimian Earthquake in the Anninghe Fault and Its Implications for Earthquake Nucleation

Seismological Research Letters ◽

10.1785/0220200332 ◽

2021 ◽

Author(s):

Tian Feng ◽

Jianping Wu ◽

Lihua Fang ◽

Xiangyun Guo ◽

Yan Cai ◽

...

Keyword(s):

Fault Plane ◽

Intraplate Earthquakes ◽

Earthquake Detection ◽

Earthquake Nucleation ◽

Stress Triggering ◽

Low Incidence ◽

Partial Overlap ◽

Occurrence Mechanism ◽

Large Earthquakes ◽

Anninghe Fault

Abstract Foreshock activity sometimes precedes large earthquakes, but how foreshocks relate to mainshock nucleation is still unclear with limited case studies existing. One way to further the understanding of the foreshock occurrence mechanism is to maximize the resolution of the foreshock characteristics by waveform-based earthquake detection and location. Here, we apply the match and locate method to scan continuous waveforms 30 days before and 44 days after the 2018 ML 4.0 Shimian earthquake in Sichuan, China, and obtain approximately three times more events than reported in a local catalog. The augmented seismicity suggests the existence of a blind small strike-slip fault deep in the east of the Anninghe fault. Forty-one foreshocks of magnitude ranging from ML−0.7 to 3.4 occurred within 4 hr before the mainshock and did not show an accelerating pattern leading up to the mainshock. Focal mechanisms are consistent between the mainshock and foreshocks, implying that the mainshock and foreshock hypocenters are located on the same fault plane. The high-precision relative locations reveal that most of the foreshocks rupture adjacent source patches along the fault plane, with little or partial overlap, which is consistent with cascade stress triggering from foreshocks to foreshocks to the mainshock. Our research is one of the few to focus on the foreshock sequence of moderate mainshocks and provides a new case for studying the mechanism of foreshocks of intraplate earthquakes with a low incidence of foreshocks.

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DynTriPy: A Python Package for Detecting Dynamic Earthquake Triggering Signals

Seismological Research Letters ◽

10.1785/0220200216 ◽

2020 ◽

Vol 92 (1) ◽

pp. 543-554

Author(s):

Naidan Yun ◽

Hongfeng Yang ◽

Shiyong Zhou

Keyword(s):

Large Scale ◽

Seismic Analysis ◽

Parallel Architecture ◽

Global Scale ◽

Earthquake Triggering ◽

Process Data ◽

Dynamic Triggering ◽

Earthquake Interaction ◽

High Level ◽

Python Package

Abstract Long-term and large-scale observations of dynamic earthquake triggering are urgently needed to understand the mechanism of earthquake interaction and assess seismic hazards. We developed a robust Python package termed DynTriPy to automatically detect dynamic triggering signals by distinguishing anomalous seismicity after the arrival of remote earthquakes. This package is an efficient implementation of the high-frequency power integral ratio algorithm, which is suitable for processing big data independent of earthquake catalogs or subjective judgments and can suppress the influence of noise and variations in the background seismicity. Finally, a confidence level of dynamic triggering (0–1) is statistically yielded. DynTriPy is designed to process data from multiple stations in parallel, taking advantage of rapidly expanding seismic arrays to monitor triggering on a global scale. Various data formats are supported, such as Seismic Analysis Code, mini Standard for Exchange of Earthquake Data (miniSEED), and SEED. To tune parameters more conveniently, we build a function to generate a database that stores power integrals in different time and frequency segments. All calculation functions possess a high-level parallel architecture, thoroughly capitalizing on available computational resources. We output and store the results of each function for continuous operation in the event of an unexpected interruption. The deployment of DynTriPy to data centers for real-time monitoring and investigating the sudden activation of any signal within a certain frequency scope has broad application prospects.

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Stress triggering of large earthquakes complicated by transient aseismic slip episodes

Journal of Geophysical Research Atmospheres ◽

10.1029/2008jb006125 ◽

2009 ◽

Vol 114 (B7) ◽

Cited By ~ 3

Author(s):

Ikuo Cho ◽

Taku Tada ◽

Yasuto Kuwahara

Keyword(s):

Aseismic Slip ◽

Stress Triggering ◽

Large Earthquakes

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Comparison of Blood Pressure in Women with and Without Premenstrual Syndrome

Shiraz E-Medical Journal ◽

10.5812/semj.111338 ◽

2021 ◽

Vol In Press (In Press) ◽

Author(s):

Hadiseh Shabdini ◽

Akram Peyman

Keyword(s):

Blood Pressure ◽

Premenstrual Syndrome ◽

Luteal Phase ◽

Blood Pressure Measurement ◽

Educational Programs ◽

Medical Sciences ◽

Significance Level ◽

Significant Difference ◽

The Common ◽

Pressure Changes

Background: Premenstrual syndrome is one of the common disorders in women, which occurs periodically in the luteal phase of the menstrual cycle. High blood pressure seems to be one of the problems that can occur with premenstrual syndrome. Objectives: This study aimed to compare blood pressure changes in two groups with and without premenstrual syndrome. Methods: This is a descriptive-comparative study. The population of the study was the students of Tehran Islamic Azad University of Medical Sciences. Data were collected using a premenstrual syndrome screening questionnaire and blood pressure measurement that were then analyzed with SPSS at a significance level of α = 0.05. Results: According to 1,408 questionnaires collected, 580 people had the premenstrual syndrome. Comparison of blood pressure before menstruation showed a significant difference between the two groups with and without premenstrual syndrome (P < 0.001). Conclusions: An increase in blood pressure in the group with premenstrual syndrome requires investigating hypertension and planning for educational programs for preventing and controlling blood pressure in people with premenstrual syndrome.

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Responding to Media Inquiries about Earthquake Triggering Interactions

Seismological Research Letters ◽

10.1785/0220200452 ◽

2021 ◽

Author(s):

Fang Fan ◽

Lingling Ye ◽

Hiroo Kanamori ◽

Thorne Lay

Keyword(s):

Long Range ◽

Aftershock Sequence ◽

Public Understanding ◽

Physical Interaction ◽

Earthquake Triggering ◽

Dynamic Triggering ◽

Long Range Interactions ◽

The Media ◽

To Come ◽

Frequency Relationship

Abstract In the aftermath of a significant earthquake, seismologists are frequently asked questions by the media and public regarding possible interactions with recent prior events, including events at great distances away, along with prospects of larger events yet to come, both locally and remotely. For regions with substantial earthquake catalogs that provide information on the regional Gutenberg–Richter magnitude–frequency relationship, Omori temporal aftershock statistical behavior, and aftershock productivity parameters, probabilistic responses can be provided for likelihood of nearby future events of larger magnitude, as well as expected behavior of the overall aftershock sequence. However, such procedures generally involve uncertain extrapolations of parameterized equations to infrequent large events and do not provide answers to inquiries about long-range interactions, either retrospectively for interaction with prior remote large events or prospectively for interaction with future remote large events. Dynamic triggering that may be involved in such long-range interactions occurs, often with significant temporal delay, but is not well understood, making it difficult to respond to related inquiries. One approach to addressing such inquiries is to provide retrospective or prospective occurrence histories for large earthquakes based on global catalogs; while not providing quantitative understanding of any physical interaction, experience-based guidance on the (typically very low) chances of causal interactions can inform public understanding of likelihood of specific scenarios they are commonly very interested in.

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Cascading elastic perturbation in Japan due to the 2012 Mw 8.6 Indian Ocean earthquake

Science Advances ◽

10.1126/sciadv.1500468 ◽

2015 ◽

Vol 1 (9) ◽

pp. e1500468 ◽

Cited By ~ 13

Author(s):

Andrew A. Delorey ◽

Kevin Chao ◽

Kazushige Obara ◽

Paul A. Johnson

Keyword(s):

Stress State ◽

Plate Tectonics ◽

Seismic Waves ◽

Crustal Material ◽

Earthquake Triggering ◽

Landers Earthquake ◽

Frictional Properties ◽

Pressure Changes ◽

Strain Transients

Since the discovery of extensive earthquake triggering occurring in response to the 1992 Mw (moment magnitude) 7.3 Landers earthquake, it is now well established that seismic waves from earthquakes can trigger other earthquakes, tremor, slow slip, and pore pressure changes. Our contention is that earthquake triggering is one manifestation of a more widespread elastic disturbance that reveals information about Earth’s stress state. Earth’s stress state is central to our understanding of both natural and anthropogenic-induced crustal processes. We show that seismic waves from distant earthquakes may perturb stresses and frictional properties on faults and elastic moduli of the crust in cascading fashion. Transient dynamic stresses place crustal material into a metastable state during which the material recovers through a process termed slow dynamics. This observation of widespread, dynamically induced elastic perturbation, including systematic migration of offshore seismicity, strain transients, and velocity transients, presents a new characterization of Earth’s elastic system that will advance our understanding of plate tectonics, seismicity, and seismic hazards.

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The Relevance of Foreshocks in Earthquake Triggering: A Statistical Study

10.20944/preprints201810.0679.v1 ◽

2018 ◽

Author(s):

Eugenio Lippiello ◽

Cataldo Godano ◽

Lucilla De Arcangelis

Keyword(s):

Statistical Study ◽

Aftershock Sequence ◽

Statistical Features ◽

Earthquake Triggering ◽

Etas Model ◽

Epidemic Type Aftershock Sequence ◽

The One ◽

Triggering Process ◽

Large Earthquakes ◽

Good Agreement

An increase of seismic activity is often observed before large earthquakes. Events responsible for this increase are usually named foreshock and their occurrence probably represents the most reliable precursory pattern. Many foreshocks statistical features can be interpreted in terms of the standard mainshock-to-aftershock triggering process and are recovered in the Epidemic Type Aftershock Sequence ETAS model. Here we present a statistical study of instrumental seismic catalogs from four different geographic regions. We focus on some common features of foreshocks in the four catalogs which cannot be reproduced by the ETAS model. In particular we find in instrumental catalogs a significantly larger number of foreshocks than the one predicted by the ETAS model. We show that this foreshock excess cannot be attributed to catalog incompleteness. We therefore propose a generalized formulation of the ETAS model, the ETAFS model, which explicitly includes foreshock occurrence. Statistical features of aftershocks and foreshocks in the ETAFS model are in very good agreement with instrumental results.

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The prognostic value of foreshocks - a statistical reevaluation

10.5194/egusphere-egu21-8691 ◽

2021 ◽

Author(s):

Ester Manganiello ◽

Marcus Herrmann ◽

Warner Marzocchi

Keyword(s):

Physical Process ◽

Large Earthquake ◽

Aftershock Sequence ◽

Earthquake Forecasting ◽

Earthquake Triggering ◽

Epidemic Type Aftershock Sequence ◽

Sequence Selection ◽

Short Time ◽

Scientific Questions ◽

Large Earthquakes

The ability to forecast large earthquakes on short time scales is strongly limited by our understanding of the earthquake nucleation process. Foreshocks represent promising seismic signals that may improve earthquake forecasting as they precede many large earthquakes. However, foreshocks can currently only be identified as such after a large earthquake occurred. This inability is because it remains unclear whether foreshocks represent a different physical process than general seismicity (i.e., mainshocks and aftershocks). Several studies compared foreshock occurrence in real and synthetic catalogs, as simulated with a well-established earthquake triggering/forecasting model called Epidemic-Type Aftershock Sequence (ETAS) that does not discriminate between foreshocks, mainshocks, and aftershocks. Some of these studies show that the spatial distribution of foreshocks encodes information about the subsequent mainshock magnitude and that foreshock activity is significantly higher than predicted by the ETAS model. These findings attribute a unique underlying physical process to foreshocks, making them potentially useful for forecasting large earthquakes. We reinvestigate these scientific questions using high-quality earthquake catalogs and study carefully the influence of subjective parameter choices and catalog artifacts on the results. For instance, we use data from different regions, account for the short-term catalog incompleteness and its spatial variability, and explore different criteria for sequence selection and foreshock definition.

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