scholarly journals Middle-Scale Ionospheric Disturbances Observed by the Oblique-Incidence Ionosonde Detection Network in North China after the 2011 Tohoku Tsunamigenic Earthquake

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 1000
Author(s):  
Jin Wang ◽  
Gang Chen ◽  
Tao Yu ◽  
Zhongxin Deng ◽  
Xiangxiang Yan ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Oblique Incidence ◽  
North China ◽  
Tohoku Earthquake ◽  
Ionospheric Disturbances ◽  
Doppler Measurement ◽  
The 2011 Tohoku Earthquake ◽  
Tsunamigenic Earthquake ◽  
The Pacific ◽  
The Pacific Ocean

The 2011 Tohoku earthquake and the following enormous tsunami caused great disturbances in the ionosphere that were observed in various regions along the Pacific Ocean. In this study, the oblique-incidence ionosonde detection network located in North China was applied to investigate the inland ionospheric disturbances related to the 2011 tsunamigenic earthquake. The ionosonde network consists of five transmitters and 20 receivers and can monitor regional ionosphere disturbances continuously and effectively. Based on the recorded electron density variations along the horizontal plane, the planar middle-scale ionospheric disturbances (MSTIDs) associated with the 2011 Tohoku tsunamigenic earthquake were detected more than 2000 km west of the epicenter about six hours later. The MSTIDs captured by the Digisonde, high-frequency (HF) Doppler measurement, and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellite provided more information about the far-field inland propagation characteristics of the westward propagating gravity waves. The results imply that the ionosonde network has the potential for remote sensing of ionospheric disturbances induced by tsunamigenic earthquakes and provide a perspective for investigating the propagation process of associated gravity waves.

Analysis of traveling ionospheric disturbances (TIDs) in GPS TEC launched by the 2011 Tohoku earthquake

Radio Science ◽  
2016 ◽  
Vol 51 (5) ◽  
pp. 507-514 ◽  
Author(s):  
Geoff Crowley ◽  
Irfan Azeem ◽  
Adam Reynolds ◽  
Timothy M. Duly ◽  
Patrick McBride ◽  
...  
Keyword(s):  
Tohoku Earthquake ◽  
2011 Tohoku Earthquake ◽  
Ionospheric Disturbances ◽  
The 2011 Tohoku Earthquake ◽  
Gps Tec ◽  
Traveling Ionospheric Disturbances

Hourly-resolution Analysis of a Mussel Shell: Influence of Normal Tide and the Great Tsunami

2021 ◽  
Author(s):  
Yuji Sano ◽  
Tomoyo Okumura ◽  
Naoko Murakami-Sugihara ◽  
Kentaro Tanaka ◽  
Takanori Kagoshima ◽  
...  
Keyword(s):  
Tohoku Earthquake ◽  
Growth Line ◽  
Mussel Shell ◽  
The 2011 Tohoku Earthquake ◽  
Northeastern Japan ◽  
The Pacific ◽  
Endogenous Clock ◽  
Mediterranean Mussel ◽  
Resolution Analysis ◽  
Cyclic Changes

Abstract We report here hourly variations of Mg/Ca, Sr/Ca and Ba/Ca ratios in a Mediterranean mussel shell (Mytilus galloprovincialis) collected at the Otsuchi bay, on the Pacific coast of northeastern Japan. This bivalve was living in the intertidal zone, where such organisms are known to form a daily or bidaily growth line comprised of abundant organic matter. Mg/Ca ratios of the inner surface of the outer shell layer, corresponding to the most recent date, show cyclic changes at 25-90 mm intervals, while no valuable variations are observed in Sr/Ca and Ba/Ca ratios. High Mg/Ca ratios were probably established when the bivalve was located at low tide with a reduced supply of Ca from seawater. Immediately following the great tsunami induced by the 2011 Tohoku earthquake, Mg/Ca enrichment occurred, up to 10 times that of normal low tide, while apparent Ba/Ca enrichment was observed for only a few days following the event, implementing a proxy of the past tsunami. Following the tsunami, periodic peaks and troughs in Mg/Ca continued, perhaps due to a biological memory effect as an endogenous clock.

scholarly journals A New Method to Improve the Detection of Co-Seismic Ionospheric Disturbances using Sequential Measurement Combination

Sensors ◽  
2019 ◽  
Vol 19 (13) ◽  
pp. 2948 ◽  
Author(s):  
Seonho Kang ◽  
Junesol Song ◽  
Deokhwa Han ◽  
Bugyeom Kim ◽  
Hyoungmin So ◽  
...  
Keyword(s):  
Time Derivative ◽  
Tohoku Earthquake ◽  
Satellite System ◽  
Detection Performance ◽  
Ionospheric Delay ◽  
New Method ◽  
Ionospheric Disturbances ◽  
The 2011 Tohoku Earthquake ◽  
Sequential Measurement ◽  
Global Navigation Satellite

Earthquakes generate energy that propagates into the ionosphere and incurs co-seismic ionospheric disturbances (CIDs), which can be observed in ionospheric delay measurements. In most cases, the CID has a weak signal strength, because the energy in the atmosphere transferred from the earthquake dissipates as it travels toward the ionosphere. It is particularly hard to observe at reference stations that are located far from the epicenter. As the number of Global Navigation Satellite System stations and their positions are restricted, it is important to employ weak CID data in the analysis by improving the detection performance of CIDs. In this study, we suggest a new method of detecting CIDs, which mainly uses a sequential measurement combination of the carrier phase-based ionospheric delay data, with a 1-second interval. The proposed method’s performance was compared with conventional methods, including band-pass filters and a representative time-derivative method, using data from the 2011 Tohoku earthquake. As a result, the maximum CID-to-noise ratio can be increased by a maximum of 13% when the proposed method is used, and consequently, the detection performance of the CID can be improved.

Analysis of Pressure and Acceleration Signals from the 2011 Tohoku Earthquake Observed by the DONET Seafloor Network

2017 ◽  
Vol 12 (1) ◽  
pp. 163-175 ◽  
Author(s):  
Hiroyuki Matsumoto ◽  
◽  
Mikhail A. Nosov ◽  
Sergey V. Kolesov ◽  
Yoshiyuki Kaneda ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Forced Oscillation ◽  
Tohoku Earthquake ◽  
Water Layer ◽  
2011 Tohoku Earthquake ◽  
Forced Oscillations ◽  
Ocean Bottom ◽  
The 2011 Tohoku Earthquake ◽  
Characteristic Frequencies ◽  
Acceleration Sensors

Ocean-bottom pressure and acceleration data simultaneously recorded by the DONET seafloor network during the 2011 Tohoku earthquake approximately 800 km from the earthquake epicenter are processed and analyzed. The close location of pressure and acceleration sensors together with the high data-sampling rate enable us to quantitatively examine and interpret pressure variations together with ocean-bottom acceleration for the first time to our knowledge. To interpret observed data, we introduce a set of characteristic frequencies that enable us to identify physical processes responsible for water layer behaviour dependent on the frequency of ocean-bottom oscillations. Explicit formulas are given for calculating all of the characteristic frequencies, which are the basis for introducing nonoverlapping frequency bands, i.e., hydroacoustic waves, forced oscillations, and gravity waves. The physical correctness of such a subdivision is confirmed by the high coherence and nearly zero phase difference between in-situ measured pressure and acceleration variations observed in the forced oscillation frequency band – a band neither hydroacoustic nor gravity waves are generated by ocean-bottom oscillation because the water layer simply follows the ocean bottom, generating forced oscillations. The dominant, long-lasting pressure fluctuations recorded by DONET during the 2011 earthquake are associated with the forced oscillation, or, more precisely, with water and sedimentary layer coupling oscillation. DONET clearly observed the 2011 Tohoku tsunami signal during more than 24 hours following the earthquake. In contrast to DART records, phase dispersion was not manifested in the tsunami signals registered by DONET.

scholarly journals Long-Term Observation of the Quasi-3-Hour Large-Scale Traveling Ionospheric Disturbances by the Oblique-Incidence Ionosonde Network in North China

Sensors ◽  
2021 ◽  
Vol 22 (1) ◽  
pp. 233
Author(s):  
Ruijiao Zhang ◽  
Gang Chen ◽  
Yaxian Li ◽  
Shaodong Zhang ◽  
Wanlin Gong ◽  
...  
Keyword(s):  
Oblique Incidence ◽  
Large Scale ◽  
North China ◽  
Statistical Characteristics ◽  
Ionospheric Disturbances ◽  
Quiet Time ◽  
Traveling Ionospheric Disturbances ◽  
Unique System ◽  
To Come ◽  
Long Term Observation

The oblique-incidence ionosonde network in North China is a very unique system for regional ionospheric observation. It contains 5 transmitters and 20 receivers, and it has 99 ionospheric observation points between 22.40° N and 33.19° N geomagnetic latitudes. The data of the ionosonde network were used to investigate the statistical characteristics of the quasi-3-h large-scale traveling ionospheric disturbances (LSTIDs). From September 2009 to August 2011, 157 cases of the quiet-time LSTIDs were recorded; 110 cases traveled southward, 46 cases traveled southwestward and only 1 case traveled southeastward. The LSTIDs mainly appeared between 10:00 and 19:00 LT in the months from September to the following May. We compared the data of the Beijing, Mohe and Yakutsk digisondes and found that the LSTIDs are most likely to come from the northern auroral region. These LSTIDs may be induced by the atmospheric gravity waves (AGWs) and presented obvious seasonal and diurnal varying features, indicating that the thermospheric wind field has played an important role.

Site-Specific Behavior of 2011 Tohoku Earthquake Tsunami Influenced by Artificial Changes of Coastal Environments

2012 ◽  
Vol 7 (sp) ◽  
pp. 485-490
Author(s):  
Chiharu Mizuki ◽  
◽  
Kazuomi Hirakawa ◽  
Keyword(s):  
Land Use ◽  
Pacific Coast ◽  
Tohoku Earthquake ◽  
2011 Tohoku Earthquake ◽  
Coastal Environments ◽  
Specific Behavior ◽  
The 2011 Tohoku Earthquake ◽  
Site Specific ◽  
The Pacific ◽  
Artificial Changes

Many aspects affect local tsunami behavior. A drastic change in behavior in the 2011 Tohoku Earthquake at specific sites in relation to coastal conditions in Hokkaido. These include coastal constructions such as jetty ports, digging formula ports, types of seawall, etc., in addition to land use for fisheries. Examples of site-specific behavior in the 2011 Tohoku Earthquake along the Pacific coast of Hokkaido are introduced in order to help future tsunami disasters.

scholarly journals Observing wave packets generated by solar terminator in TEC during typhoons

2018 ◽  
Vol 4 (2) ◽  
pp. 33-40
Author(s):  
Илья Едемский ◽  
Ilya Edemsky ◽  
Анна Ясюкевич ◽  
Anna Yasyukevich
Keyword(s):  
Tropical Cyclones ◽  
Wave Packets ◽  
Maximum Amplitude ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Total Electron ◽  
The Pacific ◽  
Typhoon Center ◽  
The Pacific Ocean ◽  
Solar Terminator

In this work, we study ionospheric disturbances excited by the passage of the solar terminator (ST) during tropical cyclones, using total electron content (TEC) data. We have considered 16 intense tropical cyclones (typhoons) that acted in the northwest of the Pacific Ocean near the territory of Japan. We analyze two-dimensional distributions of the number of registered wave packets (WPs) depending on various parameters: local time, WP maximum amplitude, and distance to typhoon. It is shown that in most cases the maximum number of WPs is observed at a distance less than 500–1500 km from the typhoon center and near the time of evening solar terminator passage. For typhoons occurring during autumn periods, the maximum number of WPs is recorded at daytime, and, apparently, is not associated with ST. Distributions of the number of WPs depending on their amplitude have a similar form for all the cases considered, with a maximum of about 0.2 TECU. At the same time, for some typhoons there are a large number of WPs with amplitude up to 0.6–0.8 TECU, which is significantly higher than WP amplitudes under quiet conditions. We briefly discuss the mechanism of possible interaction between ionospheric disturbances caused by two different sources (tropical cyclones and ST passage).

scholarly journals First GPS TEC maps of ionospheric disturbances induced by reflected tsunami waves: The Tohoku case study

2016 ◽  
Author(s):  
L. Tang ◽  
Y. Zhao ◽  
J. An
Keyword(s):  
Gravity Waves ◽  
Arrival Time ◽  
Tohoku Earthquake ◽  
Internal Gravity Waves ◽  
Ionospheric Disturbances ◽  
Propagation Characteristics ◽  
Tsunami Waves ◽  
Travelling Ionospheric Disturbances ◽  
Ionospheric Height

Abstract. The straight tsunami waves from epicenter can be reflected when they reach to coasts or underwater obstacles. In this study, we present the first ionospheric maps of reflected tsunami signature caused by the great 11 March 2011 Tohoku earthquake using the dense GPS network GEONET in Japan. We observed tsunami-like travelling ionospheric disturbances (TIDs) with similar propagation characteristics in terms of waveform, horizontal velocity, direction, period and arrival time compared to the reflected tsunami at the sea-level, indicating the TIDs are induced by the reflected tsunami. The results confirm the atmospheric internal gravity waves (IGWs) produced by reflected tsunami can also propagate upward to the atmosphere and interact with the plasma at the ionospheric height.

Empirical Fragility Curves of Buildings in Northern Miyagi Prefecture During the 2011 off the Pacific Coast of Tohoku Earthquake

2016 ◽  
Vol 11 (6) ◽  
pp. 1253-1270 ◽  
Author(s):  
Hao Wu ◽  
◽  
Kazuaki Masaki ◽  
Kojiro Irikura ◽  
Susumu Kurahashi ◽  
...  
Keyword(s):  
Pacific Coast ◽  
Fragility Curves ◽  
Ground Motions ◽  
Strong Motion ◽  
Tohoku Earthquake ◽  
2011 Tohoku Earthquake ◽  
The 2011 Tohoku Earthquake ◽  
Kobe Earthquake ◽  
The Pacific ◽  
Miyagi Prefecture

In this study, empirical fragility curves expressed in terms of relationship between damage ratio indices of buildings and ground motion indices were developed in northern Miyagi prefecture located in near-field areas during the 2011 off the Pacific coast of Tohoku Earthquake. The ground motion indices were evaluated from observed ground motions at strong-motion stations and estimated at sites at which no strong-motion accelerometers were deployed during the mainshock. The ground motions at the non-instrumental sites were estimated using the empirical Green’s function method based on bedrock motions inverted from observed records on surfaces from small events that occurred inside the source fault, transfer functions due to underground velocity structures identified from microtremor H/V spectral ratios, and a short-period source model of the mainshock. The findings indicated that the empirical fragility curves as functions of Japan Meteorological Agency (JMA) instrumental seismic intensity during the 2011 Tohoku Earthquake almost corresponded to those during the 1995 Kobe Earthquake and the seven disastrous earthquakes that occurred between 2003 and 2008. However, the empirical fragility curves as functions of peak ground velocity were the lowest. A possible reason for this is that the response spectra of the ground motions in the period ranging from 1.0 s to 1.5 s were small during the 2011 Tohoku Earthquake. Another reason could be the seismic resistant capacities of buildings in the studied districts involved during the 2011 Tohoku Earthquake exceeded those in the cities affected during the 1995 Kobe Earthquake.

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