186 research outputs found
Seismic receiver function data of Aceh, Indonesia
No full textThis dataset archives P-wave receiver functions derived from seismograms of 155 Z-land short-period nodal stations and 2 broadband stations deployed in Aceh, northern Sumatra
Dataset for Maduo Earthquake rupture imaging
No full textThis dataset includes: 1. teleseismic broadband waveform, 2. regional broadband waveforms 3. InSAR/SAR 4. 3D surface deformation data for the 2021 Mw7.4 Maduo earthquake in Chin
Systematic Comparison of InSAR and Seismic Source Models for Moderate‐Size Earthquakes in Western China: Implication to the Seismogenic Capacity of the Shallow Crust
No full textEarthquake source parameters are important for understanding earthquake physics and crustal fault properties. However, strong trade-offs between parameters (e.g., depth and origin time) and a lack of accurate velocity models and near-field seismic stations could cause large uncertainties of these parameters in seismic catalogs, particularly for shallow events. To further improve the resolution of earthquake source parameters, we use Interferometric Synthetic Aperture Radar (InSAR) images to derive source solutions of 33 moderate-size (Mw 4.1–6.6) earthquakes that occurred at shallow depths (<20 km) from November 2014 to July 2020 in western China. After evaluating the uncertainties of the InSAR solutions, we systematically compare the location, centroid depth, focal mechanism and magnitude from InSAR models with that from seismic catalogs. We find that all seismic catalogs generally report deeper (4–10 km) hypocenters or centroid depths. The uncertainties of moment tensor solutions are partially related to the percentage of the non-double-couple components in the seismic catalogs. The InSAR solutions indicate that considerable seismic moments (i.e., ∼ (Formula presented.) Nm) were released in the uppermost crust (i.e., <5 km) in a period of ∼6 years, which is not resolvable in the seismic catalogs. The smooth seismic moment distribution along depth indicates a gradual change of the frictional properties from the surface to the middle crust. As most of the studied earthquakes are located on secondary and/or unmapped faults, these findings imply a considerable portion of velocity-weakening friction in the uppermost crust along immature, secondary fault systems, which should be included in the seismic hazard evaluation.Ministry of Education (MOE)Published versionHeng Luo and Teng Wang are supported by the National Natural Science Foundation of China (41974017 and U1939202). Shengji Wei was supported by the Singapore MOE project (MOE2019-T2-1-182) and the Earth Observatory of Singapore via its funding from the National Research Foundation Singapore and the Singapore Ministry of Education under the Research Centres of Excellence initiative
Deriving centimeter-level coseismic deformation and fault geometries of small-to-moderate earthquakes from time-series Sentinel-1 SAR images
No full textSmall-to-moderate earthquakes (e.g. ≤Mw5.5) occur much more frequently than large ones (e.g. >Mw6.0), yet are difficult to study with InSAR due to their weak surface deformation that are severely contaminated by atmospheric delays. Here we propose a stacking method using time-series SAR images that can effectively suppress atmospheric phase screens and extract weak coseismic deformation in centimeter to sub-centimeter level. Using this method, we successfully derive coseismic surface deformations for three small-to-moderate (Mw∼5) earthquakes in Tibet Plateau and Tienshan region from time-series Sentinel-1 SAR images, with peak line-of-sight deformation ranging from 5–6 mm to 13 mm. We also propose a strategy to downsample interferograms with weak deformation signal based on quadtree mesh obtained from preliminary slip model. With the downsampled datasets, we invert for the centroid locations, fault geometries and slips of these events. Our results demonstrate the potential of using time-series InSAR images to enrich earthquake catalog with geodetic observations for further study of earthquake cycle and active tectonics.Nanyang Technological UniversityPublished versionThis work was supported by the National Key Research and Development Program of China (Grant No. 2019YFC1509201) and the National Science Foundation of China (NSFC Grant Nos. U1939202 and 41974017). Shengji Wei is partially supported by Earth Observatory of Singapore grant 04MNS001909A620
Predictive factors and clinical efficacy of Chinese medicine Shengji ointment in the treatment of diabetic foot ulcers in the elderly: a prospective study
No full textObjective: This study aims to investigate the predictive factors and efficacy of traditional Chinese medicine Shengji Ointment in the treatment of diabetic foot ulcers in the elderly population, with the intent of formulating an effective predictive model for deep diabetic foot ulcer healing. The importance of this research lies in its provision of new perspectives and tools for addressing the severe health impact of diabetic foot ulcers in the elderly population, considering the complexity and diversity of its treatment methods.Methods: The study includes 180 elderly patients with Wagner grade 3-4 diabetic foot ulcers that involve the tendon or fascia. The dependent variable is the initiation time of granulation tissue development. Independent variables encompass demographic information, a treatment strategy including Shengji Ointment, pre-treatment trauma assessment data, routine blood count, and biochemical index test results. Lasso regression is employed for variable selection, and Cox regression is utilized for the construction of a prediction model. A nomogram is generated to authenticate the model.Results: The Chinese Medicine treatment approach, ulcer location, creatinine levels, BMI, and haemoglobin levels are identified as independent predictors of granulation tissue development in diabetic foot ulcers. The combined treatment of Chinese herbal Shengji ointment and bromelain positively influenced granulation tissue development. The location of plantar ulcers, impaired renal functionality, obesity, and anaemia are established as independent risk factors that might influence the speed and probability of ulcer healing. The area under the time-dependent ROC curve fluctuates between 0.7 and 0.8, demonstrating substantial discrimination and calibration of the model.Conclusion: The study ascertains that a combined treatment strategy incorporating Shengji Ointment demonstrates greater effectiveness than the use of cleansing gel debridement alone in facilitating the healing of Wagner grade 3 or higher diabetic foot ulcers. Furthermore, the predictive model developed in this research serves as a valuable tool in evaluating the efficacy of Chinese Medicine treatments like Shengji Ointment for diabetic foot ulcers in the elderly. It aids clinicians in effectively assessing and adjusting treatment strategies, thereby proving its significant application value in clinical practice.Clinical Trial Registration: (https://www.chictr.org.cn/hvshowproject.html?id=73862&v=1.5&u_atoken=b403af53-d3b9-41ae-a7e2-db5498609b0c&u_asession=01tNh69p235bMUO4CmHIXcv8Hxirl5-557Duue9QB5lGfl3mf8IvPlcs2kN2zC30voX0KNBwm7Lovlpxjd_P_q4JsKWYrT3W_NKPr8w6oU7K_AyPrQhedMUWBMR2-ZDL_KO0uwDPR9XlF566xraDvT9mBkFo3NEHBv0PZUm6pbxQU&u_asig=05Kd_Q8fjv-24MVbZpOS9ef3xuCCN-tSVH5eUoJKgNLM7E0-n0zMpW6xLq9gh9aUhkKEEA15rdDoCydncF99APBwVSaTPgEG_V_B1iT4wimdCTxV_4ZVbTlDewxyQtE4YgU4-Oza7KPi94RJ64Utel0yZfqg3Tlm-bVxFNOY-zXFP9JS7q8ZD7Xtz2Ly-b0kmuyAKRFSVJkkdwVUnyHAIJzSYJ6SfhFl0WMTCCasZ7zV2I2qfyrp5m-SELPVeREKgX_6yRmLu26qT8kGfcS-Yaeu3h9VXwMyh6PgyDIVSG1W-7D_Sko5YQtpDbs3uvezYkZcUUY4o9-zDPaoYelmMDs8u7I4TPvtCXaPp44YUJcQ9bHr-_RmKA5V8nji3daArhmWspDxyAEEo4kbsryBKb9Q&u_aref=NNH1nHSUCE6pNvCilV%2F1MD0aERs%3D), identifier (ChiCTR2000039327)
Focal mechanism of the August 18th 2012 Mw6.3 Palu-Koro earthquake and its implication of seismic hazard
No full textThe Palu-Koro fault is a left-lateral strike-slip fault in Sulawesi within the active triple junction generated by the ongoing fast convergence of the Pacific-Philippine plate, the Indo-Australian plate and the Sunda plate. There are densely populated areas that are susceptible to earthquakes occur along the fault, and the August 18th 2012, Mw6.3 earthquake is one of such events. To better understand this earthquake and the seismic hazard in the region, we estimated source parameters of this earthquake using the Cut and Paste (CAP) inversion method with regional broadband waveform data. Our results show that the best solution of this event is 339°, 71°, −16° and 11 km for strike, dip, rake and centroid depth, respectively. Inversions using stations within different distance ranges, i.e. 0-5, 0-10° and 0-20°, reveal consistent solutions, suggesting the robustness of our result, which is also in agreement with that from the other agencies, i.e. USGS and Global CMT. We further verify the centroid depth by modeling the depth phases recorded at the teleseismic distance, which also confirm the depth of 11km. Finally we analyzed the Coulomb stress caused by this earthquake and historical events to investigate the interaction between the earthquakes in the region. Our analysis also shows that the unclamping effect from the 1996 Mw7.9 megathrust in the Minahassa Trench promoted the occurrence of the 2012 Mw6.3 event. High slip-rate across the fault and Coulomb stress analysis suggest that more attention should be paid to the segments along the Palu-Koro fault that did not rupture in the previous earthquake circle.Published versio
The 2015 Gorkha, Nepal, earthquake sequence : II. broadband simulation of ground motion in Kathmandu
No full textThe relatively low damage in the Kathmandu Valley caused by the 2015 Mw 7.8 Gorkha earthquake has attracted much attention. To gain a deeper understanding of this phenomenon, we conduct broadband ground‐motion simulations for both the mainshock and the Mw 7.2 Dolakha aftershock through a hybrid method that combines deterministic 3D synthetics at relatively low frequencies (0.3 Hz). Because they are summarized in a companion paper (Wei et al., 2018), the 3D deterministic synthetics were generated by embedding a finite‐fault rupture model in a 3D velocity model that is characterized by a simplified basin structure for the Kathmandu Valley. We tested different weighting schemes using a finite slip model and backprojection results to weight the high‐frequency sources. Our simulations were guided by fitting the observations from five strong‐motion stations in Kathmandu Valley and the intensity and mortality distributions. Site effects were handled by amplitude spectra ratio derived from the vertical component of a hard‐rock station (KTP). Our broadband ground‐motion simulations show that (1) the stress parameter (3.8 MPa) of the mainshock was much lower in comparison to the Mw 7.2 aftershock (23 MPa) that suggests the rupture process of the mainshock was relatively deficient in radiating high‐frequency energy and different fault friction property between the mainshock and the aftershock; (2) the soft deposits in the Kathmandu Valley experienced a pervasive nonlinear site response during the mainshock and the Mw 7.2 aftershock, which also contributed to the reduction of high‐frequency motions; and (3) the high‐frequency ground motions during the mainshock were primarily radiated from the down‐dip rupture. Hence, we suggest considering the difference in the distribution of high‐frequency radiation and fault slip in the broadband ground‐motion simulations for scenario and historical earthquakes.Ministry of Education (MOE)Nanyang Technological UniversityNational Research Foundation (NRF)This work is supported by the Earth Observatory of Singapore (EOS), Nanyang Technological University through its funding (M4430239.B50). This research is partly supported by the National Research Foundation Singapore and the Singapore Ministry of Education under the Research Centres of Excellence initiative
Exploring earthquake kinematics and physics using high-frequency seismic waves
No full textThe high-resolution source imaging of large earthquakes is vital for understanding earthquake physics, seismogenic environments, and seismic hazards. Back-projection (BP) is a commonly used technique to reveal how large earthquakes release high-frequency (HF) seismic energy, which is the primary source of severe ground shaking. This dissertation focuses on enhancing the resolution of BP to advance our knowledge of earthquakes.
I first investigate how various factors, including earthquake depth, focal mechanism complexity, and source-side 3D structure, can introduce uncertainties in BP results. Then a novel travel-time calibration strategy is proposed to improve BP resolution by lessening the influence of source-side 3D structures on travel times. The calibrated BP is employed to image the rupture processes of two crustal strike-slip events: the 2002 Mw7.9 Denali and the 2021 Mw7.4 Maduo earthquakes, both featured with clear surface ruptures. Our results demonstrate excellent consistency with independent observations, including surface ruptures and near-fault seismic data.
The calibrated BP method is further applied to study several large earthquakes, including the the 2019 Mw8.0 Peru earthquake, 2021 Mw8.1 Kermadec earthquake and the 2023 Mw7.7&Mw7.7 earthquake doublet. Comparing BP result with the coseismic slip distribution of the Peru earthquake suggests strong frequency-dependent rupture, with the largest slip patch radiating weakest HF seismic energy, suggesting strong dynamic weakening which could be attributed to thermal pressurization.
The 2021 Kermadec earthquake unusually opened the slab-mantle contact, with HF seismic energy emanating from the up-dip boundary of the coseismic slip and located right beneath the slab-forearc Moho
intersection, contrasting with typical megathrust earthquakes. This phenomenon suggests a novel seismogenic environment in the Kermadec region and the HF radiation is linked to with strong material contrast transitioning from slab-crust to slab-mantle contact, possibly associated with serpentinization in the forearc mantle wedge.
The 2023 Turkey earthquake doublet exhibits diverse rupture dynamics. The Mw7.8 event dislocates a plate boundary fault asymmetrically with a super-shear and generalized Rayleigh propagating speeds to the northwest and southwest, respectively. Conversely, the Mw7.6 event ruptures intraplate faults bilaterally in a more symmetrical manner, with both super-shear rupture speeds toward the east and west. The different symmetries during the Mw7.8 and 7.7 events can be attributed to strong and moderate material contrasts across the hosting faults, respectively, highlighting the significant influence of fault zone velocity structures on rupture dynamics.
The newly developed method significantly advances our understanding of earthquake physics and seismogenic environments. Moreover, it holds promise for near real-time high-resolution source imaging of large earthquakes in seismically active regions.Doctor of Philosoph
Exploring overlooked factors in seismic hazard evaluation of subduction zones: examples from the Himalaya
No full textSeismic hazard assessments rely on the available knowledge and constraints that can be applied, including various observations and a thorough understanding of regional structures and tectonics. However, these assessments are subject to various sources of uncertainty. These uncertainties may arise from incomplete knowledge, limited data resolution, or the use of simplified assumptions in standard frameworks for evaluating seismic hazards. This study primarily examines publications and quantifies the potential reduction of seismic moment caused by previously unconsidered structural effect–duplex structures at the depth of the Himalayan orogeny. This study also evaluates the uncertainty that may result from the subjective interpretation of seismic reflection images in the frontal Himalaya.Doctor of Philosoph
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