Early assessment of seismic hazard in terms of Voronezh massif-Moscow Depression contact

Purpose is to develop a system approach for early assessment of areas being of high seismic hazard and characterizing by low stability of rock mass relative to external loads. Methods. Well cores have been assessed down to 30 depth and seismic observations have been accumulated. Complexes of field geophysics methods have been applied for the research as well as remote sensing materials, digital model of surface relief, and techniques of qualitative and quantitative interpretation. Findings. Seismic hazard map has been formed in terms of seismic intensification and ground displacement units. The abovementioned is quite reliable but a cost-based result involving early assessments of high seismic hazard areas to infill network of geophysical measurements in the neighbourhood of the areas for their further quantitative characterization. It has been identified that rare well network and definite geophysical lines, run under conditions of a complex terrain, cannot localize the areas of high seismic hazard to focus builders on the enforcement of certain components of the erected structures. It has been defined that end result of the prognostic developments takes a shape of mapping of local areas with the decreased stability of upper share of the geological section supported by further measurements by means of a common depth point method (CDP). Comparison of potential secondary earthquake sources with high permeability zones makes it possible to predict highly reliable areas of the increased seismic magnitude. Originality.For the first time, interpretation techniques have been adapted to describe parametrically nonpotential geofields (i.e. optical density of remote basis; and relative elevation), accepted during the steps of potential field processing, with the use of wave analogies. Practical implications.The methods have been developed helping optimize field geological and geophysical operations in terms of area and well number as well as measuring stakes under the conditions of the limited prior data amount.

Deaggregation of Probabilistic Seismic Hazard and Construction of Pseudo-Exact Conditional Spectrum for China

For mainland China, the primary obstacle in conditional spectrum (CS) based ground motion selection work is that the corresponding seismic hazard deaggregation results were not released for the China national standard GB 18306- 2015 “Seismic Ground Motion Parameter Zonation Map”, which refers to the fifth-generation seismic hazard map. Therefore, this study firstly constructed a probabilistic seismic hazard map for mainland China using the three level seismicity source models as applied to produce the fifth-generation seismic hazard map. The derived peak ground acceleration (PGA) values in our seismic hazard map were basically consistent with the fifth-generation seismic hazard map for most of the 34 principal Chinese cities considered. Then, three-dimensional deaggregation scheme was performed for PGA and 5%-damped spectral acceleration (Sa) corresponding to mean return periods of 475 and 2475 years. Based on the magnitude-longitude-latitude deaggregation results of three example cities: Xichang, Kunming, and Xi’an, approximate and pseudo-exact conditional spectrum were established with/without considering multiple casual earthquakes and possible strike directions of the potential source areas. The mean pseudo-exact CS lies between the results of approximate CS using long and short axis GMMs. The conditional standard deviation of pseudo-exact CS is approximately 1.1 to 1.5 times larger than the approximate CS for the periods away from the conditional period. For three example cities, hazard consistency of the spectral accelerations of the ground motion realizations matching target distribution of pseudo-exact CS and geometric mean approximate CS were evaluated and validated. Moreover, for the 34 studied cities, we tabulated the uniform hazard curve and deaggregation results for PGA and Sa values (0.2, 0.3, 0.5, 0.7, 1.0, 1.5, and 2.0s) at MRPs of 475 and 2475 years. (https://github.com/JIKUN1990/China-Seismic-Hazard-Deaggregation-34cities)

An Overview of Earthquake Science in Malaysia

This paper highlights the level of earthquake hazard in Malaysia, the challenges in mitigating earthquake hazard and the way forward on how to strengthen earthquake science in Malaysia. Earthquake hazard is regarded as low throughout Malaysia, with the exception of Sabah where it is considered moderate. This elevated level of a hazard was reinforced during the 2015 Ranau Earthquake, which killed 18 people. Despite this and other recent sizeable earthquakes, the earthquake hazard in Malaysia is poorly understood, yet the population has increased, and growth in buildings and infrastructure has risen. While much progress has been made since the 2015 Ranau earthquake in terms of the development of (i) national seismic hazard map; (ii) national seismic building code; and (iii) planning guideline in a high-risk earthquake area, there are still many challenges faced in mitigating earthquake hazard in Malaysia. There is still a lack of seismic, geological, geodetic and engineering data; insufficient seismic and geodetic monitoring network system; lack of trained human resources; and lack of public awareness. To ensure that earthquake hazard is properly quantified and mitigated some steps have to be taken, which includes (i) comprehensive geological, geotechnical and engineering studies; (ii) coordinated seismic and geodetic monitoring; (iii) human resource capacity building; (iv) coordinated public education; (v) allocation of special research and development grant; and (vi) setting up of a National Earthquake Research Centre.

When color theory meets seismology: Principled visualization design for seismic hazard maps

<p>Probabilistic seismic hazard estimates are a key ingredient of earthquake risk mitigation strategies and are usually communicated through seismic hazard maps. Though evidence exists that visual design properties are key for effective communication using such maps, few authors describe their approach in visualizing seismic hazard. Current maps use colors, legends and data classification schemes which are suboptimal, from the visualization perspective. As such, they have the danger of miscommunicating seismic hazard. We present a set of principles regarding color choice, legend design, and classification of the continuous hazard estimate for categorical mapping. These principles are based on (1) communication goals for the seismic hazard phenomenon, (2) empirically-validated recommendations from the visualization literature and (3) other best practices in map design. We discuss the process of redesigning the German seismic hazard map using these principles. A set of prototype maps adhering to these principles are presented. We also describe ongoing efforts to test the redesigned maps, as well as how to use them to further communicate the uncertainty around probabilistic hazard estimates.</p>

Risk-targeted Maps for Spain

Many studies have demonstrated that the design of structures in the region through the uniform hazard principle does not guarantee the uniform collapse risk. Even in those regions with similar PGAs corresponding to the same mean return period, the seismic risk in terms of failure probability will be significantly different due to the structural capacity uncertainty. In this paper, the newly introduced method, known as risk targeting, is being explored in Spain using the recently updated seismic hazard map. Since risk targeting involves multiple input parameters such as model parameters of fragility curves, their variability is considered through their probability distribution corresponding to the RC moment frame building, which is the most common typology in Spain. The influence of variation of these parameters on the risk results are investigated and different assumptions for estimating the model parameters of fragility curves are illustrated. These assumptions are included in a fixed fragility curve (generic) or building-site-specific fragility curves. Different acceptable risk levels (i.e., collapse and yielding) were considered concerning the Spain seismicity level. Finally, the maps for risk-targeted design ground motion and risk coefficient are presented. It was outlined since the shape of the hazard curve across Spain is different and considering the uncertainty of structural capacity; the employment of risk-targeted analysis led to the modifications for existing design ground motions. Moreover, it was found that using the building- and site-specific fragility curves could provide better results.

Performance based evaluation of an existing continuous reinforced concrete bridge – a case study

A performance-based evaluation was conducted on an eleven-span reinforced concrete bridge located in a high seismicity area. This bridge was designed using SNI 2833:1992 and to be checked using the updated Indonesian seismic hazard map. In addition, a non-linear time history analysis was conducted using eleven pairs of ground motions to evaluate the structural performance of the bridge pier for the anticipated service life. Elastic analysis shows that the existing bridge still satisfies the strength and serviceability requirement despite the increase in seismic demand. Meanwhile, by evaluating the average inelastic longitudinal reinforcement and concrete strain at bridge pier for selected eleven ground motions, this study suggests that the bridge is still “fully operational” and “life safety” when subjected to the lower level (100 year return period) and upper level (1000 year return period) ground motions, respectively.

Towards improving the seismic hazard map and the response spectrum for the state of RN/Brazil

Although Brazilian seismic activity is defined as low to moderate, it is known that intraplate earthquakes can also be associated to high intensities. In Brazil, the state of Rio Grande do Norte (RN) is one of the most seismically active areas, but there is no specific study to evaluate the seismic hazard in this region. This paper presents analyses towards improving the seismic hazard map, the peak ground acceleration value and the response spectrum of RN. The methodology is based on Probabilistic Seismic Hazard Analysis, comparing the results to the design criteria defined in the Brazilian code NBR 15421:2006 (Design of seismic resistant structures – Procedure). The analyses show that, in general, the code sets conservative values for the peak ground acceleration and for the design response spectrum; however, related to this last one, the shape is quite different.

Improving Paleoseismic Earthquake Magnitude Estimates with Rupture Length Information: Application to the Puget Lowland, Washington State, U.S.A.

ABSTRACT Both earthquake displacement and rupture length correlate with magnitude, and, therefore, observations of each from past earthquakes can be used to estimate the magnitude of those earthquakes in the absence of instrumental records. We extend the Bayesian inversion method of Biasi and Weldon (2006), which estimates paleoearthquake magnitude from displacement observations, to incorporate both rupture length and surface displacement measurements into the magnitude inversion. We then use this method on 27 late-Pleistocene to Holocene paleoearthquakes in the Puget Lowland region of Washington. Observations of (typically vertical) fault separation per event range from 0.6 to 7 m, implying net displacement per event of up to 10±4 m for the largest event. Rupture lengths are estimated to vary between the smallest contiguous mapped scarps to the full extent of the faults mapped from geology and geophysical observations. Although, a few of the ruptures may be longer than 150 km, the ruptures have a median of 53 km, indicating that earthquakes in the Puget Lowland have relatively high displacement-to-length ratios. By considering both datasets, we find that all events were between M 6.3 and 7.5, generally consistent with the expected seismicity from the U.S. Geological Survey National Seismic Hazard Map for the region. The simultaneous use of both length and displacement data in the magnitude inversion decreases both the estimated earthquake magnitudes and the uncertainty. The magnitude reduction, in particular, is due to the relatively short rupture lengths possible for Puget Lowland faults. This implies a decrease in the seismic hazard (relative to a displacement-only assessment) to a highly populated and rapidly urbanizing region.

Discovery of Ulaanbaatar Fault: A New Earthquake Threat to the Capital of Mongolia

Destructive large earthquakes occur not only along major plate boundaries but also within the interior of plates. To establish appropriate safety measures, identifying intraplate active faults and the potential magnitude of associated earthquakes is essential before an earthquake occurs. This study was conducted to document the geomorphic expression of a previously unrecognized 50-km-long active fault in Ulaanbaatar, the capital of Mongolia. Mapping of the fault was accomplished using the Advanced Land Observation Satellite elevation dataset provided by Japan Aerospace Exploration Agency (JAXA), a stereo-scope interpretation of CORONA satellite images, the emplacement of trenches across the fault trace, and field study. The Ulaanbaatar fault (UBF) is marked by fault scarps on the surface and left-lateral stream deflections. The fault displaces late Pleistocene deposits and is thus considered to be active. Based on the length of the fault, the UBF is believed to be capable of causing earthquakes with magnitudes greater than M 7 and subsequent associated damage to buildings and heavy causalities within the metropolitan area. We strongly suggest that building resistance requirements in Ulaanbaatar should be revised to mitigate for the potential of extensive seismic damage. The results of this study can be used to revise the seismic hazard map and stipulate a new disaster prevention strategy to improve public safety in Ulaanbaatar. It is also possible that there may be other active faults in the vicinity of Ulaanbaatar, and these require investigation.