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  • 1
    Electronic Resource
    Electronic Resource
    Temporal variation of codaQ during Hualien earthquake of 1986 in eastern Taiwan (1989)
    Springer
    Pure and applied geophysics 130 (1989), S. 617-634 
    Details
    ISSN: 1420-9136
    Keywords: CodaQ ; envelope decay curve ; temporal variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The May 20, 1986, Hualien earthquake sequence occurred on the northeastern coast of Taiwan. TheM=6.1 (GS mb) mainshock was followed by a large number of closely-clustered aftershocks with the largest being anM=5.5 event. One seismic station, TWD of the Taiwan Telemetered Seismographic Network, is located in the surface projection of the source region and provides excellent recordings of the entire earthquake sequence. These recordings, plus events occurring in the same source area preceding the mainshock, offer a unique opportunity to study the spatial and temporal variations of codaQ in a region of active subduction. A simple technique is devised that uses the envelope of the coda waveform to enable a quick determination of the codaQ from drum records. For recordings with a peak power at about 8 Hz, the following findings have been obtained: 1. The ambient codaQ near an active subduction region was as low as 145; 2. There was no significant decrease in codaQ within the period beginning one year and four months prior to the mainshock; 3. There was a significant drop of codaQ immediately after the mainshock; this drop lasted approximately two days before returning to the ambient level; 4. CodaQ values varied with focal depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00881601
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    Paper (German National Licenses)
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  • 2
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    Probabilistic Seismic Hazard Analysis at Regional and National Scales: State of the Art and Future Challenges (2020)
    American Geophysical Union
    Details
    Publication Date: 2020-09-01
    Description: Seismic hazard modeling is a multidisciplinary science that aims to forecast earthquake occurrence and its resultant ground shaking. Such models consist of a probabilistic framework that quantifies uncertainty across a complex system; typically, this includes at least two model components developed from Earth science: seismic source and ground motion models. Although there is no scientific prescription for the forecast length, the most common probabilistic seismic hazard analyses consider forecasting windows of 30 to 50 years, which are typically an engineering demand for building code purposes. These types of analyses are the topic of this review paper. Although the core methods and assumptions of seismic hazard modeling have largely remained unchanged for more than 50 years, we review the most recent initiatives, which face the difficult task of meeting both the increasingly sophisticated demands of society and keeping pace with advances in scientific understanding. A need for more accurate and spatially precise hazard forecasting must be balanced with increased quantification of uncertainty and new challenges such as moving from time‐independent hazard to forecasts that are time dependent and specific to the time period of interest. Meeting these challenges requires the development of science‐driven models, which integrate all information available, the adoption of proper mathematical frameworks to quantify the different types of uncertainties in the hazard model, and the development of a proper testing phase of the model to quantify its consistency and skill. We review the state of the art of the National Seismic Hazard Modeling and how the most innovative approaches try to address future challenges.
    Description: Published
    Description: e2019RG000653
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    Apparent activation energy and rate-limiting process estimation from natural shale deformed by pressure solution in shallow subduction zone (2009)
    Elsevier
    In:  Earth and Planetary Science Letters, 287 (1/2). pp. 57-63.
    Details
    Publication Date: 2017-02-09
    Description: Pressure solution is one of the main deformation mechanisms for lithify and stress release in the rocks from shallow subduction zones. We observed temperature-dependent pressure solution development in naturally deformed shale in Shimanto accretionary complex in southwest Japan. The pressure solution develops with shear-dominated or co-axial-dominated deformation. We evaluated apparent activation energy by applying the constitutive equation of pressure solution creep to the temperature-dependent relations. The activation energy of each deformation type was estimated as 18 kJ mol− 1 for shear-dominated and 45 kJ mol− 1 for co-axial-dominated shale. The energies enable us to speculate rate-limiting processes of pressure solution i.e. dissolution, diffusion and precipitation, by comparing the energies obtained in this study with energies had been measured by experiments. The lower activation energy estimated here was similar with that of diffusion. The similarity indicates that possible rate-limiting process of shale deformation in shallow subduction zone would be diffusion. The difference of energy between deformation types can be explained by distinctive grain boundary structure.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.epsl.2009.07.032
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Towards real-time regional earthquake simulation I: real-time moment tensor monitoring (RMT) for regional events in Taiwan (2013)
    Oxford University Press
    Details
    Publication Date: 2013-12-19
    Description: We have developed a real-time moment tensor monitoring system (RMT) which takes advantage of a grid-based moment tensor inversion technique and real-time broad-band seismic recordings to automatically monitor earthquake activities in the vicinity of Taiwan. The centroid moment tensor (CMT) inversion technique and a grid search scheme are applied to obtain the information of earthquake source parameters, including the event origin time, hypocentral location, moment magnitude and focal mechanism. All of these source parameters can be determined simultaneously within 117 s after the occurrence of an earthquake. The monitoring area involves the entire Taiwan Island and the offshore region, which covers the area of 119.3°E to 123.0°E and 21.0°N to 26.0°N, with a depth from 6 to 136 km. A 3-D grid system is implemented in the monitoring area with a uniform horizontal interval of 0.1° and a vertical interval of 10 km. The inversion procedure is based on a 1-D Green's function database calculated by the frequency–wavenumber ( fk ) method. We compare our results with the Central Weather Bureau (CWB) catalogue data for earthquakes occurred between 2010 and 2012. The average differences between event origin time and hypocentral location are less than 2 s and 10 km, respectively. The focal mechanisms determined by RMT are also comparable with the Broadband Array in Taiwan for Seismology (BATS) CMT solutions. These results indicate that the RMT system is realizable and efficient to monitor local seismic activities. In addition, the time needed to obtain all the point source parameters is reduced substantially compared to routine earthquake reports. By connecting RMT with a real-time online earthquake simulation (ROS) system, all the source parameters will be forwarded to the ROS to make the real-time earthquake simulation feasible. The RMT has operated offline (2010–2011) and online (since January 2012 to present) at the Institute of Earth Sciences (IES), Academia Sinica ( http://rmt.earth.sinica.edu.tw ). The long-term goal of this system is to provide real-time source information for rapid seismic hazard assessment during large earthquakes.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 5
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    Evidence for non-self-similarity of microearthquakes recorded at a Taiwan borehole seismometer array (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-29
    Description: We investigate the relationship between seismic moment M 0 and source duration t w of microearthquakes by using high-quality seismic data recorded with a vertical borehole array installed in central Taiwan. We apply a waveform cross-correlation method to the three-component records and identify several event clusters with high waveform similarity, with event magnitudes ranging from 0.3 to 2.0. Three clusters—Clusters A, B and C—contain 11, 8 and 6 events with similar waveforms, respectively. To determine how M 0 scales with t w , we remove path effects by using a path-averaged Q . The results indicate a nearly constant t w for events within each cluster, regardless of M 0 , with mean values of t w being 0.058, 0.056 and 0.034 s for Clusters A, B and C, respectively. Constant t w , independent of M 0 , violates the commonly used scaling relation ${t_w} \propto M_0^{1/3}$ . This constant duration may arise either because all events in a cluster are hosted on the same isolated seismogenic patch, or because the events are driven by external factors of constant duration, such as fluid injections into the fault zone. It may also be related to the earthquake nucleation size.
    Keywords: Seismology
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 6
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    Efficient waveform inversion for average earthquake rupture in three-dimensional structures (2014)
    Oxford University Press
    Details
    Publication Date: 2014-07-04
    Description: Advances in observational, theoretical and computational technologies have made it possible for automatic, real-time solutions of the focal mechanisms of earthquake point sources. However, for earthquakes of moderate and greater magnitudes, the complexity of the source kinematic processes often requires additional characteristics on the source rupture in order to make seismotectonic inferences and to explain the observed directivity effects of the radiation of seismic energy. We develop an efficient and effective approach to determining the average finite-rupture models of moderate earthquakes by fitting synthetic and recorded broadband waveforms. A Green's tensor database is established using 3-D structural model with surface topography to enable rapid evaluations of accurate synthetic seismograms needed for source parameter inversions without the need for high-performance computing. We take a two-step strategy: In the first step, a point-source model is determined by a grid search for the best fault-plane solution. Then, taking the two nodal planes in the point-source model as candidates of the actual fault plane, a second grid search is carried out over a suite of simplified finite-rupture models to determine the optimal direction and speed of the integrated rupture of the finite source. We applied our method to four moderate events ( M W 6) in southeastern Taiwan. Results show that our technique provides an effective choice in semi-automatic, near real-time determinations of finite-source parameters for earthquake hazard assessment and mitigation purposes.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 7
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    Dynamic Rupture Simulation of the 2008 Mw 7.9 Wenchuan Earthquake with Heterogeneous Initial Stress (2012)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2012-08-01
    Description: The rupture process and tectonic surroundings of the 2008 Wenchuan, China, earthquake are both complex in a way that might be related to the heterogeneous stress field of the Longmen Shan region. In this study, we construct dynamic models with heterogeneous initial stress to reproduce a kinematic inversion result by Wen et al. (2012) and investigate the physical mechanisms of the variable slip pattern and rupture velocity in this event. The results show that, for the 2008 Wenchuan earthquake, (1) the rupture behavior and slip pattern can be explained by heterogeneities in initial stress and (2) the variations of rupture velocity and ground-motion pattern are strongly affected by both stress drop and fault strength. Our preferred dynamic model agrees with the kinematic model that the 2008 Wenchuan earthquake initiated with a slow velocity in the southwest, sped up in the segment with the largest slip, and then slowed down for the remaining propagation to the northeast.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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  • 8
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    Risk factors for survival in patients with von Hippel-Lindau disease (2018)
    BMJ Publishing Group
    Details
    Publication Date: 2018-04-28
    Description: Background Historically, von Hippel-Lindau (VHL) disease is characterised by a poor survival. Although genotype–phenotype correlation has been described in many studies, the risk factors for VHL survival remain unclear. This study aims to evaluate the median survival of Chinese patients with VHL disease and explore whether VHL survival is influenced by genetic and clinical factors. Methods In this retrospective study, we recruited 340 patients from 127 VHL families. Kaplan-Meier plot and Cox regression model were used to evaluate the median survival and assess how survival was influenced by birth year, birth order, sex, family history, mutation type, onset age and first presenting symptom. Results The estimated median life expectancy for Chinese patients with VHL disease was 62 years. Patients with early-onset age, positive family history and truncating mutation types had poorer overall and VHL-related survival. Patients with haemangioblastoma as their first presenting symptom were related to a higher risk of death from central nervous system haemangioblastoma than those with abdominal lesions (HR 8.84, 95% CI 2.04 to 38.37, P=0.004). Conclusions This largest VHL survival analysis indicates that onset age, family history, mutation type and first presenting symptom have an effect on the survival of patients with VHL disease, which is helpful to genetic counselling and clinical decision-making.
    Print ISSN: 0022-2593
    Electronic ISSN: 1468-6244
    Topics: Medicine
    Published by BMJ Publishing Group
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