The China Seismo-Electromagnetic Satellite (CSES), with a sun-synchronous orbit at 507 km altitude, was launched on 2 February 2018 to investigate pre-earthquake ionospheric anomalies (PEIAs) and ionospheric space weather. The CSES probes manifest longitudinal features of four-peak plasma density and three plasma depletions in the equatorial/low-latitudes as well as mid-latitude troughs. CSES plasma and the total electron content (TEC) of the global ionosphere map (GIM) are used to study PEIAs associated with a destructive M7.0 earthquake and its followed M6.5 and M6.3/M6.9 earthquakes in Lombok, Indonesia, on 5, 17, and 19 August 2018, respectively, as well as to examine ionospheric disturbances induced by an intense storm with the Dst index of − 175 nT on 26 August 2018. Anomalous increases (decreases) in the GIM TEC and CSES plasma density (temperature) frequently appear specifically over the epicenter days 1–5 before the M7.0 earthquake and followed earthquakes, when the geomagnetic conditions of these PEIA periods are relatively quiet, Dst: − 37 to 19 nT. In contrast, TEC and CSES plasma parameter anomalies occur globally in the southern hemisphere during the storm days of 26–28 August 2018. The CSES ion velocity shows that the electric fields of PEIAs associated with the M7.0 earthquake are 0.21/0.06 mV/m eastward and 0.11/0.10 mV/m downward at post-midnight/post-noon on 1–3 August 2018, while the penetration electric fields during the storm periods of 26–28 August 2018 are 0.17/0.45 mV/m westward/downward at post-midnight of 02:00 LT and 0.26/0.26 mV/m eastward/upward at post-noon of 14:00 LT. Spatial analyses on CSES plasma discriminate PEIAs from global effects and locate the epicenter of possible forthcoming large earthquakes. CSES ion velocities are useful to derive PEIA- and storm-related electric fields in the ionosphere.
{"title":"Spatial analyses on pre-earthquake ionospheric anomalies and magnetic storms observed by China seismo-electromagnetic satellite in August 2018","authors":"Jann-Yenq Tiger Liu, Xuhui Shen, Fu-Yuan Chang, Yuh-Ing Chen, Yang-Yi Sun, Chieh-Hung Chen, Sergey Pulinets, Katsumi Hattori, Dimitar Ouzounov, Valerio Tramutoli, Michel Parrot, Wei-Sheng Chen, Cheng-Yan Liu, Fei Zhang, Dapeng Liu, Xue-Min Zhang, Rui Yan, Qiao Wang","doi":"10.1186/s40562-024-00320-2","DOIUrl":"https://doi.org/10.1186/s40562-024-00320-2","url":null,"abstract":"The China Seismo-Electromagnetic Satellite (CSES), with a sun-synchronous orbit at 507 km altitude, was launched on 2 February 2018 to investigate pre-earthquake ionospheric anomalies (PEIAs) and ionospheric space weather. The CSES probes manifest longitudinal features of four-peak plasma density and three plasma depletions in the equatorial/low-latitudes as well as mid-latitude troughs. CSES plasma and the total electron content (TEC) of the global ionosphere map (GIM) are used to study PEIAs associated with a destructive M7.0 earthquake and its followed M6.5 and M6.3/M6.9 earthquakes in Lombok, Indonesia, on 5, 17, and 19 August 2018, respectively, as well as to examine ionospheric disturbances induced by an intense storm with the Dst index of − 175 nT on 26 August 2018. Anomalous increases (decreases) in the GIM TEC and CSES plasma density (temperature) frequently appear specifically over the epicenter days 1–5 before the M7.0 earthquake and followed earthquakes, when the geomagnetic conditions of these PEIA periods are relatively quiet, Dst: − 37 to 19 nT. In contrast, TEC and CSES plasma parameter anomalies occur globally in the southern hemisphere during the storm days of 26–28 August 2018. The CSES ion velocity shows that the electric fields of PEIAs associated with the M7.0 earthquake are 0.21/0.06 mV/m eastward and 0.11/0.10 mV/m downward at post-midnight/post-noon on 1–3 August 2018, while the penetration electric fields during the storm periods of 26–28 August 2018 are 0.17/0.45 mV/m westward/downward at post-midnight of 02:00 LT and 0.26/0.26 mV/m eastward/upward at post-noon of 14:00 LT. Spatial analyses on CSES plasma discriminate PEIAs from global effects and locate the epicenter of possible forthcoming large earthquakes. CSES ion velocities are useful to derive PEIA- and storm-related electric fields in the ionosphere. ","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"2 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139508785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-19DOI: 10.1186/s40562-023-00318-2
Kaya Iwamoto, Nobuaki Suenaga, Shoichi Yoshioka, Francisco Ortega-Culaciati
In southern Chile, the Nazca plate is subducting beneath the South American plate. This region was struck by megathrust earthquakes in 1960 and 2010 and is characterized by the existence of a volcanic chain. In this region, we modeled a three-dimensional thermal structure associated with the subduction of the Nazca plate by using numerical simulations. Based on the obtained temperature distribution, we determined the updip and downdip limit temperatures for the region ruptured by these two megathrust earthquakes. In addition, the distributions of water content and dehydration gradient were calculated by using appropriate phase diagrams and compared with the location of the volcanic chain. As a result, we infer that the coseismic slip of the 2010 Mw8.8 Maule earthquake occurred only at temperatures lower than and around the 350 °C isotherm that resembles the beginning of the brittle‒ductile transition. We also deduce that the rupture of the 1960 Mw9.5 Valdivia earthquake propagated up to the 450 °C isotherm because the magnitude was considerably large and the young hot plate subducted near the Chile Ridge. In addition, the hydrous minerals in the turbidites, MORB and ultramafic rocks released fluids via dehydration reactions, and dehydrated water migrated upward almost vertically, decreasing the melting point of the mantle wedge and contributing to the formation of the volcanic chain.
在智利南部，纳斯卡板块正在向南美板块下方俯冲。该地区曾在 1960 年和 2010 年发生过特大推力地震，其特点是存在火山链。在这一地区，我们通过数值模拟建立了与纳斯卡板块俯冲相关的三维热结构模型。根据得到的温度分布，我们确定了这两次大地壳地震断裂区域的上升和下降极限温度。此外，我们还利用适当的相图计算了含水量和脱水梯度的分布，并与火山链的位置进行了比较。因此，我们推断 2010 年 Mw8.8 莫尔地震的共震滑动只发生在低于 350 °C 等温线及其附近的温度下，而该等温线类似于脆性-韧性转变的起点。我们还推断，1960 年 Mw9.5 瓦尔迪维亚地震的断裂传播温度高达 450 ° C 等温线，因为震级相当大，年轻的热板块俯冲到智利海脊附近。此外，浊积岩、MORB和超基性岩中的含水矿物通过脱水反应释放出流体，脱水后的水几乎垂直向上迁移，降低了地幔楔的熔点，促进了火山链的形成。
{"title":"3D thermal structural and dehydration modeling in the southern Chile subduction zone and its relationship to interplate earthquakes and the volcanic chain","authors":"Kaya Iwamoto, Nobuaki Suenaga, Shoichi Yoshioka, Francisco Ortega-Culaciati","doi":"10.1186/s40562-023-00318-2","DOIUrl":"https://doi.org/10.1186/s40562-023-00318-2","url":null,"abstract":"In southern Chile, the Nazca plate is subducting beneath the South American plate. This region was struck by megathrust earthquakes in 1960 and 2010 and is characterized by the existence of a volcanic chain. In this region, we modeled a three-dimensional thermal structure associated with the subduction of the Nazca plate by using numerical simulations. Based on the obtained temperature distribution, we determined the updip and downdip limit temperatures for the region ruptured by these two megathrust earthquakes. In addition, the distributions of water content and dehydration gradient were calculated by using appropriate phase diagrams and compared with the location of the volcanic chain. As a result, we infer that the coseismic slip of the 2010 Mw8.8 Maule earthquake occurred only at temperatures lower than and around the 350 °C isotherm that resembles the beginning of the brittle‒ductile transition. We also deduce that the rupture of the 1960 Mw9.5 Valdivia earthquake propagated up to the 450 °C isotherm because the magnitude was considerably large and the young hot plate subducted near the Chile Ridge. In addition, the hydrous minerals in the turbidites, MORB and ultramafic rocks released fluids via dehydration reactions, and dehydrated water migrated upward almost vertically, decreasing the melting point of the mantle wedge and contributing to the formation of the volcanic chain.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"5 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139500798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-18DOI: 10.1186/s40562-023-00317-3
Yutao Jing, Chi Feng, Taisheng Chen, Yuanli Zhu, Changpeng Li, Bangyi Tao, Qingjun Song
The East China Sea (ECS) has experienced severe harmful algal blooms (HABs) that have deleterious ecological effects on marine organisms. Recent studies indicated that deploying of a second geostationary ocean color imager (GOCI-II) can significantly improve ocean monitoring. This study systematically assessed GOCI-II and its ability to detect HABs and distinguish between dinoflagellates and diatoms in the ECS. First, the remote-sensing reflectance ( $${R}_{rs}left(lambda right),$$ $$lambda$$ represents the wavelength) obtained from GOCI-II was compared to the local measurement data. Compared to the bands at 412 and 443 nm, the bands at 490, 510, and 620 nm exhibited excellent consistency, which is important for HAB detection. Second, four different methods were employed to extract bloom areas in the ECS: red tide index (RI), spectral shape (SS), red band line height ratio (LHR), and algal bloom ratio ( $${R}_{AB}$$ ). The SS (510) algorithm was the most applicable for detecting blooms from GOCI-II imagery. Finally, the classification capability of GOCI-II for dinoflagellates and diatoms was evaluated using three existing algorithms: the bloom index (BI), combined $$Prorocentrum donghaiens$$ index (PDI) and diatom index (DI), and the spectral slope ( $${R}_{_slope}$$ ). The BI algorithm yielded more satisfactory results than the other algorithms.
{"title":"Use of GOCI-II images for detection of harmful algal blooms in the East China Sea","authors":"Yutao Jing, Chi Feng, Taisheng Chen, Yuanli Zhu, Changpeng Li, Bangyi Tao, Qingjun Song","doi":"10.1186/s40562-023-00317-3","DOIUrl":"https://doi.org/10.1186/s40562-023-00317-3","url":null,"abstract":"The East China Sea (ECS) has experienced severe harmful algal blooms (HABs) that have deleterious ecological effects on marine organisms. Recent studies indicated that deploying of a second geostationary ocean color imager (GOCI-II) can significantly improve ocean monitoring. This study systematically assessed GOCI-II and its ability to detect HABs and distinguish between dinoflagellates and diatoms in the ECS. First, the remote-sensing reflectance ( $${R}_{rs}left(lambda right),$$ $$lambda$$ represents the wavelength) obtained from GOCI-II was compared to the local measurement data. Compared to the bands at 412 and 443 nm, the bands at 490, 510, and 620 nm exhibited excellent consistency, which is important for HAB detection. Second, four different methods were employed to extract bloom areas in the ECS: red tide index (RI), spectral shape (SS), red band line height ratio (LHR), and algal bloom ratio ( $${R}_{AB}$$ ). The SS (510) algorithm was the most applicable for detecting blooms from GOCI-II imagery. Finally, the classification capability of GOCI-II for dinoflagellates and diatoms was evaluated using three existing algorithms: the bloom index (BI), combined $$Prorocentrum donghaiens$$ index (PDI) and diatom index (DI), and the spectral slope ( $${R}_{_slope}$$ ). The BI algorithm yielded more satisfactory results than the other algorithms.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"21 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139501027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To reduce the uncertainty estimation of clouds and improve the forecast of surface shortwave radiation (SSR) over the Tibetan Plateau, a new cloud assimilation system is proposed which is the first attempt to directly apply the four-dimensional local ensemble transform Kalman filter method to assimilate the cloud optical thickness (COT). The high-resolution spatial and temporal data assimilated from the next-generation geostationary satellite Himawari-8, with the high-assimilation frequency, realized an accurate estimation of the clouds and radiation forecasting. The COT and SSR were significantly improved after the assimilation by independent verification. The correlation coefficient (CORR) of the SSR was increased by 11.3%, and the root-mean-square error (RMSE) and mean bias error (MBE) were decreased by 28.5% and 58.9%, respectively. The 2-h cycle assimilation forecast results show that the overestimation of SSR has been effectively reduced using the assimilation system. These findings demonstrate the high potential of this assimilation technique in forecasting of SSR in numerical weather prediction. The ultimate goal that to improve the model forecast through the assimilation of cloud properties requires further studies to achieve.
为减少云量估计的不确定性，改善青藏高原地面短波辐射预报，首次尝试直接应用四维局部集合变换卡尔曼滤波法同化云光学厚度（COT），提出了一种新的云同化系统。利用新一代地球静止卫星 "向日葵8号 "提供的高分辨率时空数据和高同化频率，实现了对云的精确估算和辐射预报。通过独立验证，同化后的 COT 和 SSR 有了明显改善。SSR的相关系数（CORR）提高了11.3%，均方根误差（RMSE）和平均偏差误差（MBE）分别降低了28.5%和58.9%。2 小时周期同化预报结果显示，同化系统有效降低了 SSR 的高估。这些研究结果表明，同化技术在数值天气预报中预报 SSR 方面具有很大的潜力。通过云特性同化来改进模式预报的最终目标还需要进一步的研究来实现。
{"title":"Estimating hourly surface shortwave radiation over northeast of the Tibetan Plateau by assimilating Himawari-8 cloud optical thickness","authors":"Tianyu Zhang, Husi Letu, Tie Dai, Chong Shi, Yonghui Lei, Yiran Peng, Yanluan Lin, Liangfu Chen, Jiancheng Shi, Wei Tian, Guangyu Shi","doi":"10.1186/s40562-023-00312-8","DOIUrl":"https://doi.org/10.1186/s40562-023-00312-8","url":null,"abstract":"To reduce the uncertainty estimation of clouds and improve the forecast of surface shortwave radiation (SSR) over the Tibetan Plateau, a new cloud assimilation system is proposed which is the first attempt to directly apply the four-dimensional local ensemble transform Kalman filter method to assimilate the cloud optical thickness (COT). The high-resolution spatial and temporal data assimilated from the next-generation geostationary satellite Himawari-8, with the high-assimilation frequency, realized an accurate estimation of the clouds and radiation forecasting. The COT and SSR were significantly improved after the assimilation by independent verification. The correlation coefficient (CORR) of the SSR was increased by 11.3%, and the root-mean-square error (RMSE) and mean bias error (MBE) were decreased by 28.5% and 58.9%, respectively. The 2-h cycle assimilation forecast results show that the overestimation of SSR has been effectively reduced using the assimilation system. These findings demonstrate the high potential of this assimilation technique in forecasting of SSR in numerical weather prediction. The ultimate goal that to improve the model forecast through the assimilation of cloud properties requires further studies to achieve.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"3 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139092614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Indonesian seas, with their complex passages and vigorous mixing, constitute the only route and are critical in regulating Pacific-Indian Ocean interchange, air-sea interaction, and global climate events. Previous research employing remote sensing and numerical simulations strongly suggested that this mixing is tidally driven and localized in narrow channels and straits, with only a few direct observations to validate it. The current study offers the first comprehensive temporal microstructure observations in the south of Lombok Strait with a radius of 0.05° and centered on 115.54oE and 9.02oS. Fifteen days of tidal mixing observations measured potential temperature and density, salinity, and turbulent energy dissipation rate. The results revealed significant mixing and verified the remotely sensed technique. The south Lombok temporal and depth averaged of the turbulent kinetic energy dissipation rate, and the diapycnal diffusivity from 20 to 250 m are = 4.15 ± 15.9) × 10-6 W kg-1 and = (1.44 ± 10.7) × 10-2 m2s-1, respectively. This is up to 104 times larger than the Banda Sea [ = (9.2 ± 0.55) × 10-6 m2s-1] (Alford et al. Geophys Res Lett 26:2741-2744, 1999) or the "open ocean" = 0.03 × 10-4 m2s-1 within 2° of the equator to (0.4-0.5) × 10-4 m2s-1 at 50°-70° (Kunze et al. J Phys Oceanogr 36:1553-1576, 2006). Therefore, nonlinear interactions between internal tides, tidally induced mixing, and ITF plays a critical role regulating water mass transformation and have strong implications to longer-term variations and change of Pacific-Indian Ocean water circulation and climate.
Supplementary information: The online version contains supplementary material available at 10.1186/s40562-024-00349-3.
{"title":"Field measurements of turbulent mixing south of the Lombok Strait, Indonesia.","authors":"R Dwi Susanto, Zexun Wei, Priyadi Dwi Santoso, Guanlin Wang, Muhammad Fadli, Shujiang Li, Teguh Agustiadi, Tengfei Xu, Bayu Priyono, Ying Li, Guohong Fang","doi":"10.1186/s40562-024-00349-3","DOIUrl":"10.1186/s40562-024-00349-3","url":null,"abstract":"<p><p>The Indonesian seas, with their complex passages and vigorous mixing, constitute the only route and are critical in regulating Pacific-Indian Ocean interchange, air-sea interaction, and global climate events. Previous research employing remote sensing and numerical simulations strongly suggested that this mixing is tidally driven and localized in narrow channels and straits, with only a few direct observations to validate it. The current study offers the first comprehensive temporal microstructure observations in the south of Lombok Strait with a radius of 0.05° and centered on 115.54<sup>o</sup>E and 9.02<sup>o</sup>S. Fifteen days of tidal mixing observations measured potential temperature and density, salinity, and turbulent energy dissipation rate. The results revealed significant mixing and verified the remotely sensed technique. The south Lombok temporal and depth averaged of the turbulent kinetic energy dissipation rate, and the diapycnal diffusivity from 20 to 250 m are <math><mi>ε</mi></math> = 4.15 ± 15.9) × 10<sup>-6</sup> W kg<sup>-1</sup> and <math><mrow><mi>K</mi> <mi>ρ</mi></mrow> </math> = (1.44 ± 10.7) × 10<sup>-2</sup> m<sup>2</sup>s<sup>-1</sup>, respectively. This <math><mrow><mi>K</mi> <mi>ρ</mi></mrow> </math> is up to 10<sup>4</sup> times larger than the Banda Sea [ <math><mrow><mi>K</mi> <mi>ρ</mi></mrow> </math> = (9.2 ± 0.55) × 10<sup>-6</sup> m<sup>2</sup>s<sup>-1</sup>] (Alford et al. Geophys Res Lett 26:2741-2744, 1999) or the \"open ocean\" <math><mrow><mi>K</mi> <mi>ρ</mi></mrow> </math> = 0.03 × 10<sup>-4</sup> m<sup>2</sup>s<sup>-1</sup> within 2° of the equator to (0.4-0.5) × 10<sup>-4</sup> m<sup>2</sup>s<sup>-1</sup> at 50°-70° (Kunze et al. J Phys Oceanogr 36:1553-1576, 2006). Therefore, nonlinear interactions between internal tides, tidally induced mixing, and ITF plays a critical role regulating water mass transformation and have strong implications to longer-term variations and change of Pacific-Indian Ocean water circulation and climate.</p><p><strong>Supplementary information: </strong>The online version contains supplementary material available at 10.1186/s40562-024-00349-3.</p>","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"11 1","pages":"36"},"PeriodicalIF":4.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11324699/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142001030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-21DOI: 10.1186/s40562-023-00316-4
Yukinari Seshimo, Hiroki Kawabata, Shoichi Yoshioka, Francisco Ortega-Culaciati
We used Global Navigation Satellite System (GNSS) time series data to estimate the spatiotemporal slip distribution for a long-term slow slip event (L-SSE) that occurred in the Tokai region, central Japan, from 2012 to 2016. Since all the used GNSS data were affected by the postseismic deformation associated with the 2011 Mw9.0 Tohoku-Oki earthquake, we removed such postseismic signal from the time series of three components at each of the stations. The minimal time window for an inversion analysis was set to 0.5 years (6 months), taking into account the signal-to-noise ratio of displacements for each time window. In the horizontal displacement fields, displacements were observed in the south‒southeast and southeast directions on the west and east sides of Lake Hamana, respectively, with temporal changes in their amounts and directions. In the vertical displacement fields, uplift was observed on the east side of Lake Hamana. From these data, we estimated the L-SSE initiated in approximately 2012.5 and ended by 2017.0, indicating the duration time is 4.5 years and the duration was much longer than that obtained in a previous study. Using these data, we performed the inversion analysis, in which three a priori information were assumed, i.e., the spatial distribution of slip is smooth, slip mainly occurs in the direction of plate convergence, and the temporal variation in the slip is smooth, to obtain the spatiotemporal slip distribution on a plate boundary with 3-D geometry. As a result, we identified that the L-SSE consisted of two subevents. The first subevent initiated on the southwest side of Lake Hamana and expanded during the period from 2013.0 to 2014.5. The maximum slip velocity during the period from 2012.5 to 2017.0 was estimated to be approximately 3.5 cm/year there for 2013.5–2014.0. The second subevent took place on the west side of Lake Hamana gradually from 2015.0 to 2015.5, continued, and expanded from 2015.5 to 2016.5. From the cumulative slip distribution, we found that its shape spread in the dip direction and obtained a maximum slip of approximately 10.6 cm, a moment release of 2.7 × 1019 Nm, and an equivalent moment magnitude of 6.9. Comparing our results with the L-SSE that occurred in the Tokai region between 2000 and 2005, we found that the slip initiation location was almost the same, but the subsequent slip location was more southerly for the 2012–2016 Tokai L-SSE. Additionally, the maximum slip velocity and moment magnitude were smaller for the 2012–2016 L-SSE.
{"title":"Spatiotemporal slip distribution associated with the 2012–2016 Tokai long-term slow slip event inverted from GNSS data","authors":"Yukinari Seshimo, Hiroki Kawabata, Shoichi Yoshioka, Francisco Ortega-Culaciati","doi":"10.1186/s40562-023-00316-4","DOIUrl":"https://doi.org/10.1186/s40562-023-00316-4","url":null,"abstract":"We used Global Navigation Satellite System (GNSS) time series data to estimate the spatiotemporal slip distribution for a long-term slow slip event (L-SSE) that occurred in the Tokai region, central Japan, from 2012 to 2016. Since all the used GNSS data were affected by the postseismic deformation associated with the 2011 Mw9.0 Tohoku-Oki earthquake, we removed such postseismic signal from the time series of three components at each of the stations. The minimal time window for an inversion analysis was set to 0.5 years (6 months), taking into account the signal-to-noise ratio of displacements for each time window. In the horizontal displacement fields, displacements were observed in the south‒southeast and southeast directions on the west and east sides of Lake Hamana, respectively, with temporal changes in their amounts and directions. In the vertical displacement fields, uplift was observed on the east side of Lake Hamana. From these data, we estimated the L-SSE initiated in approximately 2012.5 and ended by 2017.0, indicating the duration time is 4.5 years and the duration was much longer than that obtained in a previous study. Using these data, we performed the inversion analysis, in which three a priori information were assumed, i.e., the spatial distribution of slip is smooth, slip mainly occurs in the direction of plate convergence, and the temporal variation in the slip is smooth, to obtain the spatiotemporal slip distribution on a plate boundary with 3-D geometry. As a result, we identified that the L-SSE consisted of two subevents. The first subevent initiated on the southwest side of Lake Hamana and expanded during the period from 2013.0 to 2014.5. The maximum slip velocity during the period from 2012.5 to 2017.0 was estimated to be approximately 3.5 cm/year there for 2013.5–2014.0. The second subevent took place on the west side of Lake Hamana gradually from 2015.0 to 2015.5, continued, and expanded from 2015.5 to 2016.5. From the cumulative slip distribution, we found that its shape spread in the dip direction and obtained a maximum slip of approximately 10.6 cm, a moment release of 2.7 × 1019 Nm, and an equivalent moment magnitude of 6.9. Comparing our results with the L-SSE that occurred in the Tokai region between 2000 and 2005, we found that the slip initiation location was almost the same, but the subsequent slip location was more southerly for the 2012–2016 Tokai L-SSE. Additionally, the maximum slip velocity and moment magnitude were smaller for the 2012–2016 L-SSE.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"250 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2023-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138826712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-11DOI: 10.1186/s40562-023-00315-5
Bo Liu, Kai Yang, Xiangwen Liu, Gang Huang, Benjamin Ng
Seasonal prediction of the Indian Ocean dipole (IOD) is important, considering its impact on the climate of surrounding regions. Here we compare the prediction of the IOD in two generations of prediction system developed by the China Meteorology Administration (CMA), i.e., the second-generation climate model prediction system (CPSv2) and CPSv3. The results show that CPSv3 has better ability to predict the variability and spatial pattern of the IOD than CPSv2, especially when the lead time is long. CPSv3 maintains a certain level of credibility when predicting IOD events with 6-month lead time. The improved data assimilation in CPSv3 has reduced the predictability error of eastern Indian Ocean sea surface temperature (SST) and contributed to improvements in IOD prediction. Enhanced simulation of the El Niño-Southern Oscillation (ENSO)–IOD relationship promotes better prediction skill of ENSO-related IOD events in CPSv3. Our results suggest that upgrading data assimilation and the simulation of the ENSO–IOD relationship are critical for improving the prediction of the IOD in coupled climate models.
{"title":"Improved Indian Ocean dipole seasonal prediction in the new generation of CMA prediction system","authors":"Bo Liu, Kai Yang, Xiangwen Liu, Gang Huang, Benjamin Ng","doi":"10.1186/s40562-023-00315-5","DOIUrl":"https://doi.org/10.1186/s40562-023-00315-5","url":null,"abstract":"Seasonal prediction of the Indian Ocean dipole (IOD) is important, considering its impact on the climate of surrounding regions. Here we compare the prediction of the IOD in two generations of prediction system developed by the China Meteorology Administration (CMA), i.e., the second-generation climate model prediction system (CPSv2) and CPSv3. The results show that CPSv3 has better ability to predict the variability and spatial pattern of the IOD than CPSv2, especially when the lead time is long. CPSv3 maintains a certain level of credibility when predicting IOD events with 6-month lead time. The improved data assimilation in CPSv3 has reduced the predictability error of eastern Indian Ocean sea surface temperature (SST) and contributed to improvements in IOD prediction. Enhanced simulation of the El Niño-Southern Oscillation (ENSO)–IOD relationship promotes better prediction skill of ENSO-related IOD events in CPSv3. Our results suggest that upgrading data assimilation and the simulation of the ENSO–IOD relationship are critical for improving the prediction of the IOD in coupled climate models.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"41 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138567410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The cumulative absolute absement (CAA) of the 3 s window after P-wave arrival can be used to estimate the magnitude ( $${M}_{CAA}$$ ) of an earthquake. This method can achieve good results even when only the six stations nearest to the epicenter are used. The standard deviation between the estimated CAA magnitude ( $${M}_{CAA}$$ ) and the moment magnitude ( $${M}_{w}$$ ) is found to be 0.3 when using either 6 or 20 stations. This means that $${M}_{CAA}$$ can be reliably predicted using the closest 6 stations. On the other hand, the magnitude ( $${M}_{Pd}$$ ) derived from $${P}_{d}$$ using the closest 20 stations has a standard deviation of 0.4 between the estimated $${M}_{Pd}$$ and $${M}_{w}$$ . This suggests that CAA is a better magnitude determination parameter for the EEW system than $${P}_{d}$$ .
{"title":"Magnitude determination using cumulative absolute absement for earthquake early warning","authors":"Yih-Min Wu, Himanshu Mittal, Yueh-Ho Lin, Yu-Hsuan Chang","doi":"10.1186/s40562-023-00314-6","DOIUrl":"https://doi.org/10.1186/s40562-023-00314-6","url":null,"abstract":"The cumulative absolute absement (CAA) of the 3 s window after P-wave arrival can be used to estimate the magnitude ( $${M}_{CAA}$$ ) of an earthquake. This method can achieve good results even when only the six stations nearest to the epicenter are used. The standard deviation between the estimated CAA magnitude ( $${M}_{CAA}$$ ) and the moment magnitude ( $${M}_{w}$$ ) is found to be 0.3 when using either 6 or 20 stations. This means that $${M}_{CAA}$$ can be reliably predicted using the closest 6 stations. On the other hand, the magnitude ( $${M}_{Pd}$$ ) derived from $${P}_{d}$$ using the closest 20 stations has a standard deviation of 0.4 between the estimated $${M}_{Pd}$$ and $${M}_{w}$$ . This suggests that CAA is a better magnitude determination parameter for the EEW system than $${P}_{d}$$ .","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"33 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138567648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-08DOI: 10.1186/s40562-023-00313-7
John C. H. Chiang, Anthony J. Broccoli
The seasonality of Earth’s climate is driven by two factors: the tilt of the Earth’s rotation axis relative to the plane of its orbit (hereafter the tilt effect), and the variation in the Earth–Sun distance due to the Earth’s elliptical orbit around the Sun (hereafter the distance effect). The seasonal insolation change between aphelion and perihelion is only ~ 7% of the annual mean and it is thus assumed that the distance effect is not relevant for the seasons. A recent modeling study by the authors and collaborators demonstrated however that the distance effect is not small for the Pacific cold tongue: it drives an annual cycle there that is dynamically distinct and ~ 1/3 of the amplitude from the known annual cycle arising from the tilt effect. The simulations also suggest that the influence of distance effect is significant and pervasive across several other regional climates, in both the tropics and extratropics. Preliminary work suggests that the distance effect works its influence through the thermal contrast between the mostly ocean hemisphere centered on the Pacific Ocean (the ‘Marine hemisphere’) and the hemisphere opposite to it centered over Africa (the ‘Continental hemisphere’), analogous to how the tilt effect drives a contrast between the northern and southern hemispheres. We argue that the distance effect should be fully considered as an annual cycle forcing in its own right in studies of Earth’s modern seasonal cycle. Separately considering the tilt and distance effects on the Earth’s seasonal cycle provides new insights into the workings of our climate system, and of direct relevance to paleoclimate where there are outstanding questions for long-term climate changes that are related to eccentricity variations.
{"title":"A role for orbital eccentricity in Earth’s seasonal climate","authors":"John C. H. Chiang, Anthony J. Broccoli","doi":"10.1186/s40562-023-00313-7","DOIUrl":"https://doi.org/10.1186/s40562-023-00313-7","url":null,"abstract":"The seasonality of Earth’s climate is driven by two factors: the tilt of the Earth’s rotation axis relative to the plane of its orbit (hereafter the tilt effect), and the variation in the Earth–Sun distance due to the Earth’s elliptical orbit around the Sun (hereafter the distance effect). The seasonal insolation change between aphelion and perihelion is only ~ 7% of the annual mean and it is thus assumed that the distance effect is not relevant for the seasons. A recent modeling study by the authors and collaborators demonstrated however that the distance effect is not small for the Pacific cold tongue: it drives an annual cycle there that is dynamically distinct and ~ 1/3 of the amplitude from the known annual cycle arising from the tilt effect. The simulations also suggest that the influence of distance effect is significant and pervasive across several other regional climates, in both the tropics and extratropics. Preliminary work suggests that the distance effect works its influence through the thermal contrast between the mostly ocean hemisphere centered on the Pacific Ocean (the ‘Marine hemisphere’) and the hemisphere opposite to it centered over Africa (the ‘Continental hemisphere’), analogous to how the tilt effect drives a contrast between the northern and southern hemispheres. We argue that the distance effect should be fully considered as an annual cycle forcing in its own right in studies of Earth’s modern seasonal cycle. Separately considering the tilt and distance effects on the Earth’s seasonal cycle provides new insights into the workings of our climate system, and of direct relevance to paleoclimate where there are outstanding questions for long-term climate changes that are related to eccentricity variations.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"85 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138560866","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.1186/s40562-023-00311-9
Abayneh Tilahun, Hayal Desta
Ethiopia faces a significant challenge in combating soil erosion. This study addresses the concern within Ada’a watershed of the Awash River basin. GIS and the Universal Soil Loss Equation (USLE) Model were used to predict soil loss and the sediment transport index (STI) in the Ada’a watershed of the Awash River basin. RUSLE model required intensive rainfall data registered continuously for 30 min, due to unavailability of this Rainfall data USLE model were preferred. Moreover, USLE model was chosen because of its straightforward methodology and accessibility to data. The study's objectives were to determine the mean annual soil loss rate, STI, and to identify and rank the most important erosion-prone spots for soil conservation planning. Using the interactive Spatial Analyst Tool Map Algebra Raster Calculator in the ArcGIS environment, the mean annual soil loss was estimated based on grid cells by multiplying the corresponding USLE factor values (R, K, LS, C, and P). The STI was also calculated on the Raster Calculator in ArcGIS using flow accumulation and slope gradients. The result shows that R, K, LS, C, and P factor values were estimated in the watershed as 344.9 to 879.65 MJ mm h−1 year−1, 0.11 to 0.38, 0% to 22.23%, 0 to 1, and 0.55 to 1, respectively. The overall annual soil loss in the watershed ranged from 0 to 457.4 tons ha−1 year−1. The Sediment Transport Index ranges from 0 to 856.193. The result implies there is increasing rate of soil losses and sediments observed at alarming rate. The highest rate of soil loss was found in the watershed’s lowest parts. Accordingly, sustainable erosion control mechanisms based on topography and land use types are highly recommended, especially in the upper part of the watershed.
{"title":"Soil erosion modeling and sediment transport index analysis using USLE and GIS techniques in Ada’a watershed, Awash River Basin, Ethiopia","authors":"Abayneh Tilahun, Hayal Desta","doi":"10.1186/s40562-023-00311-9","DOIUrl":"https://doi.org/10.1186/s40562-023-00311-9","url":null,"abstract":"Ethiopia faces a significant challenge in combating soil erosion. This study addresses the concern within Ada’a watershed of the Awash River basin. GIS and the Universal Soil Loss Equation (USLE) Model were used to predict soil loss and the sediment transport index (STI) in the Ada’a watershed of the Awash River basin. RUSLE model required intensive rainfall data registered continuously for 30 min, due to unavailability of this Rainfall data USLE model were preferred. Moreover, USLE model was chosen because of its straightforward methodology and accessibility to data. The study's objectives were to determine the mean annual soil loss rate, STI, and to identify and rank the most important erosion-prone spots for soil conservation planning. Using the interactive Spatial Analyst Tool Map Algebra Raster Calculator in the ArcGIS environment, the mean annual soil loss was estimated based on grid cells by multiplying the corresponding USLE factor values (R, K, LS, C, and P). The STI was also calculated on the Raster Calculator in ArcGIS using flow accumulation and slope gradients. The result shows that R, K, LS, C, and P factor values were estimated in the watershed as 344.9 to 879.65 MJ mm h−1 year−1, 0.11 to 0.38, 0% to 22.23%, 0 to 1, and 0.55 to 1, respectively. The overall annual soil loss in the watershed ranged from 0 to 457.4 tons ha−1 year−1. The Sediment Transport Index ranges from 0 to 856.193. The result implies there is increasing rate of soil losses and sediments observed at alarming rate. The highest rate of soil loss was found in the watershed’s lowest parts. Accordingly, sustainable erosion control mechanisms based on topography and land use types are highly recommended, especially in the upper part of the watershed.","PeriodicalId":48596,"journal":{"name":"Geoscience Letters","volume":"53 12","pages":""},"PeriodicalIF":4.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138496705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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