| PaperNO | Paper / Abstract |
|
B5-001
10:50
|
11:10
|
SEISMIC HAZARD MODELLING IN NEW ZEALAND: LESSONS FROM RECENT EARTHQUAKES
The occurrence of major damaging earthquakes in New Zealand in recent years has required urgent, regionally-focused efforts to update seismic hazard models in order for infrastructural recovery to proceed (Gerstenberger, this conference). Lessons learned from these major earthquakes have also stimulated many research efforts to improve the seismic hazard models at both national and regional scales, such as: the development of complex multi-fault earthquake sources; modelling of aperiodicity for large earthquakes in low-seismicity regions; a re-evaluation of the shape of magnitude-frequency distributions for fault sources; generation of synthetic seismograms for earthquakes in low seismicity regions; and the development of methods to evaluate the upper limits of ground motions. The methods developed for these nationally- and regionally-based studies are expected to be integrated into future seismic hazard modelling efforts in New Zealand.
Mark Stirling
hazard, New Zealand, Seismic
|
|
B5-002
11:10
|
11:30
|
APPLICATION AND UPTAKE OF TIME-DEPENDENT HAZARD ASSESSMENT IN NEW ZEALAND
Traditionally, probabilistic seismic hazard analysis (PSHA) in New Zealand and elsewhere has relied on the assumption that earthquakes are independent of one another in time and in space. In the last decade large earthquakes in New Zealand have challenged the utility of this assumption when PSHA results are used in post-earthquake decision making. Following both the 2010+ Canterbury Earthquake Sequence and the 2016 M7.8 Kaikoura earthquake, earthquake recovery and rebuild decisions were necessary that required the best estimates of seismic hazard for the next 50 years, necessarily including the significant impact of these large earthquakes on future seismicity rates. The Canterbury Seismic Hazard Model (CSHM) and Kaikoura Seismic Hazard Model (KSHM) include multiple aspects of time-dependence. Critically, they both include multiple models of both short-term (yearly) and medium-term (decadal) earthquake clustering. Additionally, multiple models of long-term background rates have been included that model uncertainties introduced by the learning catalogue and also include geodetic strain rate information. The time-dependent changes to the model have increased the hazard for both models with the CSHM largely dominated by the clustering sources and KSHM hazard controlled by a mix of clustering and traditional fault sources. Finally, the hazard results have played an important part in earthquake recovery including changes to building design guidelines and requirements for retrofitting earthquake prone buildings.
Matt Gerstenberger
Canterbury, Kaikoura, New Zealand, Seismology, Time-Dependent Hazard
|
|
B2-001
11:30
|
11:50
|
ACCELERATING FORESHOCKS OF CRUSTAL EARTHQUAKES CONTROLLED BY FRICTIONAL HETEROGENEITIES
While most earthquakes start abruptly, with no evidence for a nucleation process, accelerating foreshocks within or in the vicinity of the eventual mainshock rupture zone for some moderate to large crustal earthquakes have been documented recently. For example, Tape et al. (2018) reported nucleation signals of crustal earthquakes in the Minto Flats fault zone in central Alaska, manifested by ~20 seconds of simultaneous high-frequency foreshocks and a very low-frequency earthquake (VLFE). One potential explanation for such observations is a slow slip front propagating over the fault and triggering foreshocks as it transitions into the mainshock rupture. Another explanation may be that accelerating foreshocks represent cascading sequences of fault ruptures due to static and/or dynamic stress changes, without underlying slow slip. Here we show that a numerical fault model incorporating full inertial dynamics and rate-and-state friction laws with frictional heterogeneities can reproduce the accelerating foreshocks of crustal earthquakes in the Minto Flats fault zone in central Alaska. Our results suggest that a slow physical process, such as slow slip or fluid diffusion, in between small-scale, velocity-weakening asperities is needed to generate accelerating foreshocks. Our model further shows that the time scale of accelerating foreshock sequences depends on the degree and size of frictional heterogeneities and tectonic loading rates. Our model may also explain why the occurrence of accelerating foreshocks is relatively uncommon.
Yoshihiro Kaneko
Accelerating foreshocks, Earthquake cycle simulations, Earthquake dynamics, Frictional heterogeneities, Rate and state friction, Slow slip
|
|
A4-002
12:10
|
12:25
|
EFFECT OF SEISMIC RECORD IN NEWMARK ANALYSIS FOR EARTHQUAKE-INDUCED LARGE-SCALE LANDSLIDE
In past two decades, there are many rapid and large volume earthquake-induced landslides those caused catastrophic destroy. Earthquake-induced large landslide would usually form landslide dam or large disaster area as Tsaoling landslide and Jiufenershan landslide (the 1999 Chi-chi earthquake), Daguangbao landslide (the 2008 Wenchuan earthquake), Aso-bridge landslide (the 2016 Kumamoto earthquake), Atsuma landslides (the 2018 Hokkaido earthquake). Newmark displacement method could calculate the permanent displacement when the landslide mass slides on the discontinuities such as bedding plane or joint. This study aims to understand the effect of seismic records for the Newmark analysis of earthquake-induced landslide. Newmark analysis with velocity-displacement dependent friction law were performed for Tsaoling and Daguangbao landslides, respectively. The analysis of Tsaoling landslide uses the acceleration of CHY080 seismic station which locates at the back slope surface of Tsaoling landslide and the distance to landslide is about 500 m. The analysis result is corresponding to observations of field and seismic analysis. The analysis of Daguangbao landslide uses the acceleration of MZQP seismic station which locates at the foot wall of Yingxiu-Beichuan fault and distance to landslide is 10 km. The low permanent displacement of analysis result indicates that the high frequency seismic acceleration prevents to cumulate the permanent displacement even with the high peak ground acceleration. Besides, the site, topographic, and path effects of seismic acceleration and the spatial relationship between landslide movement direction and seismic station should be considered in the Newmark analysis.
Che-Ming Yang, Wei-An Chao, Jia-Jyun Dong
earthquake-induced landslide, ground motion acceleration, Newmark displacement method, slope structure, topographic relief, velocity-displacement dependent friction law
|
|
B5-011
12:10
|
12:25
|
LESSONS LEARNED FROM RECENT EARTHQUAKES: 2016 MEINONG, TAIWAN, 2017 PUEBLA, MEXICO, AND 2017 POHANG, SOUTH KOREA
This paper presents lessons learned from the recent earthquakes, 2016 Meinong, Taiwan (M 6.4), 2017 Puebla, Mexico (M7.1) and 2017 Pohang, South Korea (M5.5) based on the reconnaissance experiences of the author. Common structural and nonstructural failures observed in the three earthquakes are discussed and related to the design and construction practices. Also, the performances of the reinforced concrete buildings retrofitted before the earthquakes are discussed.
Insung Kim
2016 Meinong Earthquake, 2017 Pohang Earthquake,, 2017 Puebla Earthquake, nonstructural components, reconnaissance, seismic retrofit
|