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Dense and broad‐coverage ocean‐bottom observation networks enable us to obtain near‐fault displacement records associated with an offshore earthquake. However, simple integration of ocean‐bottom strong‐motion acceleration records leads to physically unrealistic displacement records. Here we propose a new method using a Kalman filter to estimate coseismic displacement waveforms using the collocated ocean‐bottom seismometers and pressure gauges. First, we evaluate our method using synthetic records and then apply it to an offshore Mw 6.0 event that generated a small tsunami. In both the synthetic and real cases, our method successfully estimates reasonable displacement waveforms. Additionally, we show that the computed waveforms improve the results of the finite fault modeling process. In other words, the proposed method will be useful for estimating the details of the rupture mechanism of offshore earthquakes as a complement to onshore observations. Plain Language Summary Ocean‐bottom observations enable us to obtain near‐fault displacement records associated with an offshore earthquake. However, simple integration of ocean‐bottom acceleration records leads to physically unrealistic displacement records. Here we propose a new method to estimate offshore coseismic displacement waveforms. First, we evaluate our method using synthetic records and then apply it to an offshore earthquake that generated a small tsunami. In both cases, our method successfully estimates reasonable displacements. Additionally, we show that the computed waveforms improve the results of the earthquake source modeling process. In other words, the proposed method will be useful for estimating the details of the rupture mechanism of offshore earthquakes as a complement to onshore observations. Key Points Propose a new method to estimate the near‐fault displacement waveform associated with an offshore earthquake Our method adopts the Kalman filter approach to combine the collocated strong‐motion seismometer and ocean‐bottom pressure gauge Since the obtained displacement waveforms have fault rupture information, it can improve the finite fault model

Ishikawa, T.; Komine, T.; Aoki, S.I., and Okabe, T., 2014. Characteristics of rip current drowning on the shores of Japan. The characteristics of rip current drowning on the shores of Japan was investigated using the analysis of the lifesaver's rescue reports of 2013 and field observations of some beaches. Although the necessary rescue equipment and the water safety information such as signboards were mostly prepared, a large amount of rip current drowning occurred. On most re-occurring rip current drowning beaches, there are permanent rips and fixed rips associated with the characteristic of topography and the coastal structures at most beaches under the relatively high wave condition. Especially, in the case lifesavers cannot determine the swimming areas, swimming areas are generally determined by the local regulations from local governments and shop owners on most beaches. The most important outbreak factor regarding the rip current drowning is the human factor such as the management problems and coastal structures, which was concluded.

In the search for precursors to earthquakes, correlation has been found between geochemical characteristics of soil gases and seismic activity. In this paper we present evidence that seismic waves can trigger emission of soil radon (Rn) and carbon dioxide (CO2). An active experiment was performed in two fault zones in China, the Annighe fault in Sichuan province and the Xiadian fault in Heibei province. An active seismic source was used to generate seismic waves at 10 m depth in wells within bedrock. Rn and CO2 detectors were placed around the wells at a distance of ∼1 m for observing the effects of the seismic waves on the emission of the gases. The observations confirm that the seismic waves have a significant and direct effect on the concentration and flux of soil radon and carbon dioxide. When the seismic events were triggered, the observed concentrations of Rn and CO2 immediately increased and reached peak values within 5–50 min and 30–60 min, with corresponding increases of Rn and CO2 concentrations by 10.5%–238.7% and 3.1%–54.1%, respectively. The measured concentrations and flux of CO2 and Rn after the passage of the seismic waves showed strong correlation, confirming the suggestion that CO2 is the carrier gas for Rn. To the best of our knowledge this is the first direct, in‐situ measurement of gas emission caused by the passage of seismic waves and provides important constraints for better understanding of geochemical earthquake precursors. Plain Language Summary Observed geochemical properties of soil gases migrated from the deep Earth can be used to survey seismicity, volcanic activity and emission of greenhouse gases. However, due to difficulty in natural earthquake prediction, most observations on the geochemical effects linked to seismic activity are conducted after or away from naturally occurring events, with the effects normally inferred from seismic parameters. In this study, an active seismic source based on methane gaseous detonation was employed to artificially produce seismic events along two fault zones, and in‐situ measurements of concentrations and flux of radon (Rn) and carbon dioxide (CO2) were conducted. These observations showed strong correlation between concentrations and flux of CO2 and Rn after the events, in agreement with the hypothesis that CO2 is the carrier gas for Rn in tectonically active settings. Key Points Soil CO2 and Rn emission triggered by a new type active source that excited at 10 m deep well in bedrock are observed at first time Quantitative effect of seismicity on the concentration and flux of soil CO2 and Rn are presented Emission of CO2 and Rn after the seismicity show strong correlation and proved that CO2 is the carrier gas for Rn

An earthquake measuring 7.7 magnitude on the Richter scale occurred at 04:17am on February 6, 2023 in the Pazarcık district of Kahramanmaraş province Turkey. In the hours following the 7.7 magnitude event in Kahramanmaraş, a second 7.6 magnitude earthquake struck the region and a third 6.4 magnitude earthquake struck Gaziantep, causing extensive damage and death. A total of ten provinces directly experienced the earthquake, including Kahramanmaraş, Hatay, Gaziantep, Osmaniye, Malatya, Adana, Diyarbakır, Şanlıurfa, Adıyaman, and Kilis. The official figures indicate 31,643 people were killed, 80,278 were injured, and 6,444 buildings were destroyed within seven days of the earthquakes (as of 12:00pm/noon on Monday, February 13th). The area affected by the earthquake has been officially declared to be 500km in diameter. This report primarily relies on observations made by pioneer Emergency Physicians (EPs) who went to the disaster areas shortly after the first earthquake (in the early stages of the disaster). According to their observations: (1) Due to winter conditions, there were transportation problems and a shortage of personnel reaching disaster areas on the first day after the disaster; (2) On the second day of the disaster, health equipment was in short supply; (3) As of the third day, health workers were unprepared in terms of knowledge and experience for the disaster; and (4) The subsequent deployment of health personnel to the disaster area was uncoordinated and unplanned on the following days, which resulted in the health personnel working there not being able to meet even their basic needs (such as food, heating, and shelter). During the first week, coordination was most frequently reported as the most significant problem.

Photovoltaic power generation is an important clean energy alternative to fossil fuels. To reduce CO 2 emissions, the Chinese government has ordered the construction of a large number of photovoltaic (PV) panels to generate power in the past two decades; many are located in desert areas because of the sufficient light conditions. Large-scale PV construction in desert areas can alter the local microclimate and soil conditions, thereby affecting the growth of vegetation. However, few studies have focused on the effects of PV panels on the environment of desert areas. In this study, we investigated the effects of PV panels on soil moisture and temperature via a whole-year field experiment at a PV power plant in a desert area in western China. The in situ soil moisture and temperature at a depth of 0–0.4 m were measured under three types of PV shading conditions: shaded by fixed-tilt (FIX) PV panels, shaded by oblique single-axis (OSA) PV panels, and no shading. The results showed that the soil temperature and moisture at sites under PV shading were significantly affected compared with those at sites without shading. PV panels increased the average soil temperature during winter but decreased it during the other three seasons. Moreover, the warming effect of FIX PV panels on the soil is more apparent than that of OSA PV panels. PV panels have positive effects on soil moisture. Compared with that at the sites without shaded areas, the average soil moisture under the FIX PV panels and under the OSA PV panels increased by 14.7% and by 11.1%, respectively. These data provide support for future studies on vegetation restoration around PV power plants in desert areas.

The present study aims to identify, characterize monitor and model the transport pathways of volcanic ashes and various features of the active phase of Barren Island volcano (BIV), Andaman and Nicobar Island, India during 2018 using the several Earth observation satellite technologies and field observations in the study area. Sentinel-2 satellite datasets have been used to identify volcanic eruption features such as lava flow, ash plume, cinder and vent and different directions of lava flow from the cinder cone during the 2018 eruptive phase of BIV. To visualize the major variations in thermal intensity and understand the behaviour of current volcanic activity, volcanic radiative power (VRP) and radiant fluxes of the recent eruptive phase were calculated using MIROVA. In addition, thermal anomaly was observed in the form of anomalous fire pixels for 44 days in FIRMS database. Also, NASA/NOAA Visible Infrared Imaging Radiometer Suite (VIIRS, VNP14IMGT) were used for validating the real-time activity of the 2018 volcanic eruption phase. The results obtained were closely related with the periods of high eruptions as observed in the Sentinel-2 datasets. The volcanic aerosol ‘sulphur dioxide’ (SO₂) data (time series-area averaged) were analysed as well as a five-day forward trajectory and volcanic ash model for each eruption event was developed using HYSPLIT model to identify the transport pathways and extent of volcanic ash cloud in the lower atmosphere during the eruptive phase of the volcano.

The landslide events, that occurred in August 2018 in the Idukki district Kerala, India were surveyed during 12–14 September 2018. Many landslides were studied through field observations to decipher their mechanism and mitigation measures have been recommended. Possible causative factors responsible for these slope failures have been discussed. This event was the most devastating disaster that affected millions of people and the second such event after the Kedarnath tragedy (2013) during this decade. The primary causes responsible for initiation of these landslides were unexpected intense rainfall, unplanned development and urbanization. This study on field observationbased interpretations will help academicians, researchers and field engineers to plan future initiatives for reconstruction planning and implementation in line with future disaster risk reduction.

In the surfzone, breaking‐wave generated eddies and vortices transport material along the coast and offshore to the continental shelf, providing a pathway from land to the ocean. Here, surfzone vorticity is investigated with unique field observations obtained during a wide range of wave and bathymetric conditions on an Atlantic Ocean beach. Small spatial‐scale [O(10 m)] vorticity estimated with a 5 m diameter ring of 14 current meters deployed in ∼2 m water depth increased as the directional spread of the wave field increased. Large spatial‐scale [O(100 m)] vorticity calculated from remote sensing estimates of currents across the surfzone along 200 m of the shoreline increased as alongshore bathymetric variability (channels, bars, bumps, holes) increased. For all bathymetric conditions, large‐scale vorticity in the inner surfzone was more energetic than in the outer surfzone. Plain Language Summary Circular, rotating flow features, such as eddies, swirls, and vortices mix and disperse material throughout the ocean. Here, circular flow features that can transport sediments, pollutants, and biota from the shore to the continental shelf were investigated using field observations from a 5 m diameter ring of current meters in 2 m depth and from tracking naturally occurring ocean foam visible in optical images of the surfzone (where waves break) spanning 200 m of the coast. The observations show that small‐scale flow patterns become more energetic as ocean waves arrive from a wider range of directions and that large‐scale flow features become more energetic as the seafloor becomes more nonuniform (including holes and channels). Key Points Surfzone vorticity is estimated for the first time with unique field observations within, across, and along the surfzone In situ observations show that small‐scale vorticity injected by breaking waves increases with wave directional spread Remotely sensed observations show large‐spatial scale vorticity increases as bathymetry becomes more alongshore inhomogeneous

The vortex settling basin for suspended sediment is a sediment treatment device that enables efficient use of irrigation water, yet the diameter design remains insufficiently defined, leading to large dis crepancies between measured and designed trapping efficiency in practice. This study proposes a diameter design method based on the tangential characteristic Reynolds number. Field observations were first conducted at three representative projects—Donglei, Talan River, and Shangmaxiangdi. Guided by these observations, laboratory physical models were developed, and an Acoustic Doppler Velocimeter was used to measure and analyze the distribution of tangential characteristic Reynolds number in each basin. The results show that when the sediment trapping efficiency is high, the tangential characteristic Reynolds number should be less than 9.5 × 10⁶ for radial positions between 0.80 and 0.92 at the 180-degree section or between 0.60 and 0.92 at the 270-degree section, where the radial position is the distance from the measurement point to the basin center divided by the basin radius. Building on this relationship, a diameter design method for the vortex settling basin for suspended sediment is proposed. Verification using prototype projects indicates that replacing the traditional empirical approach with the proposed method can increase the trapping efficiency of suspended sediment by about 9.4%–21%. These findings provide practical guidance for diameter design.

The solar cycle 23 minimum period has been characterized by a weaker solar and interplanetary magnetic field. This provides an ideal time to study how the strength of the photospheric field affects the interplanetary magnetic flux and, in particular, how much the observed interplanetary fields of different cycle minima can be understood simply from differences in the areas of the coronal holes, as opposed to differences in the surface fields within them. In this study, we invoke smaller source surface radii in the potential-field source-surface (PFSS) model to construct a consistent picture of the observed coronal holes and the near-Earth interplanetary field strength as well as polarity measurements for the cycles 23 and 22 minimum periods. Although the source surface value of 2.5  R ⊙ is typically used in PFSS applications, earlier studies have shown that using smaller source surface heights generates results that better match observations during low solar activity periods. We use photospheric field synoptic maps from Mount Wilson Observatory (MWO) and find that the values of ≈ 1.9 R ⊙ and ≈ 1.8 R ⊙ for the cycles 22 and 23 minimum periods, respectively, produce the best results. The larger coronal holes obtained for the smaller source surface radius of cycle 23 somewhat offsets the interplanetary consequences of the lower magnetic field at their photospheric footpoints. For comparison, we also use observations from the Michelson Doppler Imager (MDI) and find that the source surface radius of ≈ 1.5 R ⊙ produces better results for cycle 23, rather than ≈ 1.8 R ⊙ as suggested from MWO observations. Despite this difference, our results obtained from MWO and MDI observations show a qualitative consistency regarding the origins of the interplanetary field and suggest that users of PFSS models may want to consider using these smaller values for their source surface heights as long as the solar activity is low.