Ryosuke Azuma
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View article: Non-double-couple components of the 2024 Noto earthquake aftershocks: influence on focal mechanism estimation
Non-double-couple components of the 2024 Noto earthquake aftershocks: influence on focal mechanism estimation Open
Aftershocks of the 2024 Noto earthquake exhibited a notable discrepancy between focal mechanisms estimated from P-wave polarities and those derived from routine moment tensor (MT) analyses based on waveform inversion of regional data. Whil…
View article: Spatiotemporal variation of aftershock activity in northern source region of the 2011 Tohoku-oki earthquake by long-term ocean bottom seismometers
Spatiotemporal variation of aftershock activity in northern source region of the 2011 Tohoku-oki earthquake by long-term ocean bottom seismometers Open
A huge plate boundary earthquake eventuated between the Pacific plate and the landward plate in 2011 and was named the 2011 off the Pacific coast of Tohoku earthquake. Following the mainshock, many aftershocks were generated. It is essenti…
View article: Enhanced P-wave velocity imaging by marine airgun-source seismic surveys with distributed acoustic sensing
Enhanced P-wave velocity imaging by marine airgun-source seismic surveys with distributed acoustic sensing Open
View article: Seismic Structure Characterizing the Large Shallow Slip Zone of the 17th‐Century Kuril Earthquake
Seismic Structure Characterizing the Large Shallow Slip Zone of the 17th‐Century Kuril Earthquake Open
The southern Kuril Trench subduction zone experienced a M9‐class megathrust earthquake in the 17th century, and another is highly probable within the next 30 years. This earthquake likely exhibited large coseismic slip at the shallower pla…
View article: Precise aftershock activity in the marine source region of the 2024 Noto-Hanto earthquake by rapid response observation using ocean bottom seismometers
Precise aftershock activity in the marine source region of the 2024 Noto-Hanto earthquake by rapid response observation using ocean bottom seismometers Open
The 2024 Noto-Hanto earthquake with a magnitude of 7.6 occurred in the Noto Peninsula on January 1, 2024. The mainshock had a reverse fault focal solution and direction of compression axis was the northwest–southeast. In the Noto Peninsula…
View article: Enhanced P-wave velocity imaging by marine controlled-source seismic surveys with Distributed Acoustic Sensing
Enhanced P-wave velocity imaging by marine controlled-source seismic surveys with Distributed Acoustic Sensing Open
P-wave velocity (Vp) structures in marine areas have been estimated using marine controlled-source seismic surveys and refraction methods. The spatial resolution of Vp structures depends on the number of receivers and shots. In marine envi…
View article: Geometrical barrier determines the updip limit of slow earthquake slip
Geometrical barrier determines the updip limit of slow earthquake slip Open
Increased observations of shallow slow earthquakes have highlighted structural irregularities that explain the generation mechanisms of slow earthquakes. However, due to considerable uncertainties in the source locations of slow earthquake…
View article: Solidified magma reservoir derived from active source seismic experiments in the Aira caldera, southern Kyushu, Japan
Solidified magma reservoir derived from active source seismic experiments in the Aira caldera, southern Kyushu, Japan Open
The Aira caldera, located in southern Kyushu, Japan, originally formed 100 ka, and its current shape reflects the more recent 30 ka caldera-forming eruptions (hereafter, called the AT eruptions). This study aimed to delineate the detailed …
View article: Solidified magma reservoir derived from seismic exploration in the Aira caldera, southern Kyushu, Japan
Solidified magma reservoir derived from seismic exploration in the Aira caldera, southern Kyushu, Japan Open
Seismic exploration was conducted along a profile running through the Aira caldera located in southern Kyushu, Japan. The caldera was formed by an ignimbrite eruption approximately 30 ka BP, namely, the “AT eruption,” which produced the It…
View article: Along‐Arc Heterogeneity of the Seismic Structure Around a Large Coseismic Shallow Slip Area of the 2011 Tohoku‐Oki Earthquake: 2‐D <i>Vp</i> Structural Estimation Through an Air Gun‐Ocean Bottom Seismometer Experiment in the Japan Trench Subduction Zone
Along‐Arc Heterogeneity of the Seismic Structure Around a Large Coseismic Shallow Slip Area of the 2011 Tohoku‐Oki Earthquake: 2‐D <i>Vp</i> Structural Estimation Through an Air Gun‐Ocean Bottom Seismometer Experiment in the Japan Trench Subduction Zone Open
The 2011 Tohoku‐oki earthquake occurred with a rupture length of 500 km along the Japan Trench, causing a large slip (>30 m) at the shallowest portion of the plate boundary fault south of 39°N off Miyagi and a smaller slip (~10 m) north of…
View article: Airgun-ocean bottom seismometer survey dataset
Airgun-ocean bottom seismometer survey dataset Open
These data are the seismic waveform recordsections and the P-wave velocity model obtained by Azuma et al. (JGR, 2018), collected through an airgun-ocean bottom seismometer (OBS) survey. The recordsections of 29 OBS are 'RAW data' with no w…
View article: Airgun-ocean bottom seismometer survey dataset
Airgun-ocean bottom seismometer survey dataset Open
These data are the seismic waveform recordsections and the P-wave velocity model obtained by Azuma et al. (JGR, 2018), collected through an airgun-ocean bottom seismometer (OBS) survey. The recordsections of 29 OBS are 'RAW data' with no w…
View article: Crustal structure and origin of the Eggvin Bank west of Jan Mayen, NE Atlantic
Crustal structure and origin of the Eggvin Bank west of Jan Mayen, NE Atlantic Open
The Eggvin Bank, located between the Jan Mayen Island and Greenland, is an unusually shallow area containing several submarine volcanic peaks, confined by two transforms on the Northern Kolbeinsey Ridge (NKR). We represent P and S wave vel…
View article: Development and examination of new algorithms of traveltime detection in GPS/acoustic geodetic data for precise and automated analysis
Development and examination of new algorithms of traveltime detection in GPS/acoustic geodetic data for precise and automated analysis Open
A GPS/acoustic (GPS/A) geodetic observation technique allows us to determine far offshore plate motion in order to understand the mechanism of megathrust earthquakes. In this technique, the distance between a sea-surface platform and seafl…