第53回統計地震学セミナー / The 53rd Statistical Seismology Seminar
- Date&Time
- 2016年1月27日（水）
/ 27 January, 2016 (Wednesday) 13:30 – 15:30
- Place
- 統計数理研究所 セミナー室4 (D312B)
/ Seminar room 4 (D312B) @ The Institute of Statistical Mathematics
【13:30 –】
- Speaker1
- Dr. YIN Fengling
(Institute of Geophysics, China Earthquake Administration, Beijing, China)
- Title
- A surprise result of geothermal numerical simulation - Persistent drawdown of ground water table may reduce local climate warming rate
- Authors
- YIN Fengling, SHI Yaolin, ZHANG Huai
- Abstract
- Due to persistent groundwater over-exploitation since the 1970s, groundwater level has been found significantly declined in a large area of more than 70,000 km² in Beijing, Tianjing and Hebei Provinces in North China. Consequently, a series of geo-environmental problems have emerged and drawn widely public attentions, such as land subsidence, groundwater contamination, sea water invasion, etc. We found that decline of water table can result in significant reduction in geothermal heat flux density, and this effect has never been discussed in literatures. Thermal properties, such as thermal conductivity, specific heat, are different for layers of water saturated sediment beneath the water table and layers of dry sediments above the water table. When the water table declines, due to the variation of thermal properties, transcend changes of underground geotherm occurs. Our numerical simulation indicates that surface heat flow density may reduce 40%, about 25mW/m² in ground water drawdown zone in North China after more than 40 years over-exploitation, and the surface heat flow density cannot return to normal state for hundreds of years even if the water table does not decline any more from now on. The amount of reduction of heat flow density is small, but it can last for long period of hundreds of years, and cover a large area of 70,000 km² , its effect on climate may not be negligible. It is estimated that this reduction of surface heat flow may reduce an air column temperature 0.08℃/a if it is adiabatic with surroundings, while the actual air temperature warming rate is only 0.03℃/a in the depress zone and 0.05℃/a outside the depression zone in North China. Meteorological subsurface temperature (up to 3.2m depth) records show similar trend. Although air temperatures are influenced by many factors, but the decline of surface heat flow density should be one of the factors to be studied. We suggest that more attention should be paid to this effect, and systematic monitoring of geotherm at tens to hundred meters depth should be carried out.
【14:30 –】
- Speaker2
- Dr. Matteo Maroni
(National Institute of Geophysics and Volcanology, Rome, Lazio, Italy)
- Title
- Some recent techniques to improve earthquake forecasting
- Authors
- Matteo Taroni, Warner Marzocchi, Jeremy Zechar, Maximilian Werner
- Abstract
-
In this presentation I will show some recent results regarding the earthquake forecasting techniques. In particular I will show:
i) How to consider aftershocks and foreshocks in the seismic hazard computation, with an application to the Italian case.
ii) How to merge different catalogues to obtain a better estimation of the Tapered Gutenberg-Richter distribution parameters, with an application to the global and Italian case.
iii) How to create an ensemble model to improve the performance of the short-term earthquake forecasting models, with an application to the New Zealand case.
