scholarly journals Long-term acceleration of aseismic slip preceding the M w 9 Tohoku-oki earthquake: Constraints from repeating earthquakes

2015 ◽  
Vol 42 (22) ◽  
pp. 9717-9725 ◽  
Author(s):  
Andreas P. Mavrommatis ◽  
Paul Segall ◽  
Naoki Uchida ◽  
Kaj M. Johnson
Keyword(s):  
Aseismic Slip ◽  
Repeating Earthquakes

Repeating earthquakes follow afterslip gradient in the aftermath of the 16th April 2016 M7.8 Pedernales earthquake in Ecuador

2021 ◽  
Author(s):  
Caroline Chalumeau ◽  
Keyword(s):  
Template Matching ◽  
Earthquake Forecasting ◽  
Double Difference ◽  
Recurrence Time ◽  
Fault Mechanics ◽  
Aseismic Slip ◽  
Earthquake Triggering ◽  
Repeating Earthquakes ◽  
Waveform Cross Correlation ◽  
One Year

<p>Repeating earthquakes are earthquakes that repeatedly break a single, time-invariant fault patch. They are generally associated with aseismic slip, which is thought to load asperities, leading to repeated rupture. Repeating earthquakes are therefore useful tools to study aseismic slip and fault mechanics, with possible applications to earthquake triggering, loading rates and earthquake forecasting.</p><p>In this study, we analyze one year of aftershocks following the 16<sup>th</sup> April 2016 Mw 7.8 Pedernales earthquake in Ecuador to find repeating families, using data recorded by permanent and temporary seismological stations. In our area, seismicity during both the inter-seismic and post-seismic periods has been previously linked to aseismic slip. We calculate waveform cross-correlation coefficients (CC) on all available catalogue events, which we use to sort events into preliminary families, using a minimum CC of 0.95. These events were then stacked and used to perform template-matching on the continuous data. In total, 376 earthquakes were classified into 62 families of 4 to 15 earthquakes, including 8 from the one-year period before the mainshock. We later relocated these earthquakes using a double-difference method, which confirmed that most of them did have overlapping sources.</p><p>Repeating earthquakes seem to concentrate largely around the areas of largest afterslip release, where afterslip gradient is the highest. We also find an increase in the recurrence time of repeating events with time after the mainshock, over the first year of the postseismic period, which highlights a possible timeframe for the afterslip’s deceleration. Our results suggest that while most repeating aftershocks are linked to afterslip release, the afterslip gradient may play a bigger role in determining their location than previously thought.</p>

A Two-Scale Preparation Phase Preceded an Mw 5.8 Earthquake in the Sea of Marmara Offshore Istanbul, Turkey

2020 ◽  
Vol 91 (6) ◽  
pp. 3139-3147 ◽  
Author(s):  
Virginie Durand ◽  
Stephan Bentz ◽  
Grzegorz Kwiatek ◽  
Georg Dresen ◽  
Christopher Wollin ◽  
...  
Keyword(s):  
Matched Filter ◽  
Aseismic Slip ◽  
Sea Of Marmara ◽  
Spatiotemporal Evolution ◽  
Short Term ◽  
Filter Technique ◽  
The North ◽  
Preparation Phase ◽  
Scale Preparation

Abstract We analyze the spatiotemporal evolution of seismicity during a sequence of moderate (an Mw 4.7 foreshock and Mw 5.8 mainshock) earthquakes occurring in September 2019 at the transition between a creeping and a locked segment of the North Anatolian fault in the central Sea of Marmara, northwest Turkey. To investigate in detail the seismicity evolution, we apply a matched-filter technique to continuous waveforms, thus reducing the magnitude threshold for detection. Sequences of foreshocks preceding the two largest events are clearly seen, exhibiting two different behaviors: a long-term activation of the seismicity along the entire fault segment and a short-term concentration around the epicenters of the large events. We suggest a two-scale preparation phase, with aseismic slip preparing the mainshock final rupture a few days before, and a cascade mechanism leading to the nucleation of the mainshock. Thus, our study shows a combination of seismic and aseismic slip during the foreshock sequence changing the strength of the fault, bringing it closer to failure.

Low-Frequency Tremors Immediately After the 2011 Tohoku-Oki Earthquake Detected by Near-Trench OBS Observations

2020 ◽  
Author(s):  
Hidenobu Takahashi ◽  
Ryota Hino ◽  
Naoki Uchida ◽  
Takanori Matsuzawa ◽  
Yusaku Ohta ◽  
...  
Keyword(s):  
Near Field ◽  
Low Frequency ◽  
Spectral Shape ◽  
Ocean Bottom ◽  
Aseismic Slip ◽  
Very Low Frequency ◽  
Repeating Earthquakes ◽  
Ocean Bottom Seismometers ◽  
Repeating Earthquake ◽  
Interplate Earthquakes

Abstract We used temporal seismic observation using pop-up type ocean-bottom seismometers to detect a number of low-frequency tremors (LFTs) immediately after the 2011 Tohoku-Oki earthquake in the northern periphery of its aftershock area. The near-field observation clearly distinguished LFTs from regular earthquakes based on their spectral shape in the frequency band of 1–4 Hz. In addition to the LFTs accompanied by known very low frequency earthquakes (VLFEs), more than 130 LFTs without known VLFE activity were detected during April–October, 2011. The newly detected LFTs were in the vicinity of a sequence of small repeating earthquakes indicating mixed distribution of LFTs and regular interplate earthquakes in the region. The LFTs and repeating earthquake activities show a periodicity of 60–100 days, which is similar to that of the LFT activity in the later period (2016–2018). This suggests that the LFT activity is modulated by sustained background aseismic slip events throughout the postseismic period of the 2011 mainshock.

Analysis of the foreshock sequences preceding two moderate (Mw4.7 and Mw5.8) earthquakes in the Sea of Marmara offshore Istanbul, Turkey.

2020 ◽  
Author(s):  
Virginie Durand ◽  
Stephan Bentz ◽  
Grzegorz Kwiatek ◽  
Georg Dresen ◽  
Christopher Wollin ◽  
...  
Keyword(s):  
Stress State ◽  
Matched Filter ◽  
Preparation Process ◽  
Aseismic Slip ◽  
Sea Of Marmara ◽  
Spatiotemporal Evolution ◽  
Short Term ◽  
Filter Technique ◽  
The North

<p>In September 2019 a sequence of two moderate earthquakes (Mw4.7 and Mw5.8) occurred in the central Sea of Marmara (Turkey), SW of Istanbul. These events took place ate the transition between a creeping and a locked segment of the North Anatolian Fault. To investigate in detail the spatiotemporal evolution of the seismicity, we apply a matched-filter technique to continuous waveforms, thus reducing the magnitude threshold for detection. Sequences of foreshocks preceding the two mainshocks are clearly seen, exhibiting different behaviors: a migration of the seismicity along the entire fault segment on the long-term (several days before the mainshocks) and a concentration around the epicenters of the large events on the short-term (during the few hours preceding the mainshocks). We infer that both seismic and aseismic slip during the foreshock sequences change the stress state on the fault, bringing it closer to failure. Our observations also suggest that the Mw 4.7 event contributed to weaken the fault as part of the preparation process of the Mw 5.8 earthquake.</p>

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