下記の通り、４月の防災研地震火山グループ研究会を開催いたします。
今月は、防災研に3カ月間滞在されておりますCaltechのTom Heaton教授に震源物理の力学についてお話いただきます。
みなさま奮ってご参加ください。
４月地震火山グループ研究会
日時：４月２６日（金）14:00 - 15:30
会場：京都大学防災研究所 連携研究棟 ３階 大セミナー室
http://www.dpri.kyoto-u.ac.jp/web_j/contents/tatemono_j.html
（地図中の５番の建物です）
スピーカー：Tom Heaton 教授（カリフォルニア工科大学）
タイトル：Implications of Strong-Rate-Weakening Friction for the Length-Scale Dependence of the Strength of the Crust;
Why Earthquakes Are so Gentle
【要旨】
The thinness of fault slipping zones and the paucity of observed melts implies very low dynamic friction compared to the overburden pressure (less than 0.05 for a meter of slip at 10 km). However, if static friction was comparably low, then the crust could not support observed topographic relief. Strong-rate-weakening friction seems to be a plausible explanation for these seemingly conflicting observations. Strong-rate-weakening friction leads to slip-pulses with extremely complex failure dynamics; strong positive feedback between the slip and the friction produces multi-scale chaos. Unfortunately, 3-d continuum problems with strong-rate-weakening friction are numerically intractable. Therefore we (Ahmed Elbanna and I) investigated the much simpler problem of 1-d spring block sliders with strong-rate-weakening-friction. We show that the system produces power-law complexity. That is, the pre-stress evolves into a state that is heterogeneous at all scales. Since the pre-stress and the events are spatially heterogeneous, we must generalize our definition of “strength.” We define “stress-based strength” to be the spatial average of the pre-stress in a failure region, and we define “work-based strength” to be the average work per unit of deformation. We show that these strengths are not the same. Furthermore, we show that the larger the event (or system), the smaller the strength. We show that the strength decreases as a power with the size; the exponent of this relation is related to the dynamic heterogeneity of the system. Since the model is homogeneous, all complexity is dynamic. Earthquakes are so gentle because the Earth is so big. Finally we show a surprising new energy transport equation that reproduces the chaotic behavior of the full numerical simulation. The equation is multi-scale and many orders of magnitude faster than the full numerical system.
下記の通り、４月の防災研地震火山グループ研究会を開催いたします。
今月は、防災研に3カ月間滞在されておりますCaltechのTom Heaton教授に震源物理の力学についてお話いただきます。
みなさま奮ってご参加ください。
４月地震火山グループ研究会
日時：４月２６日（金）14:00 - 15:30
会場：京都大学防災研究所 連携研究棟 ３階 大セミナー室
http://www.dpri.kyoto-u.ac.jp/web_j/contents/tatemono_j.html
（地図中の５番の建物です）
スピーカー：Tom Heaton 教授（カリフォルニア工科大学）
タイトル：Implications of Strong-Rate-Weakening Friction for the Length-Scale Dependence of the Strength of the Crust;
Why Earthquakes Are so Gentle
【要旨】
The thinness of fault slipping zones and the paucity of observed melts implies very low dynamic friction compared to the overburden pressure (less than 0.05 for a meter of slip at 10 km). However, if static friction was comparably low, then the crust could not support observed topographic relief. Strong-rate-weakening friction seems to be a plausible explanation for these seemingly conflicting observations. Strong-rate-weakening friction leads to slip-pulses with extremely complex failure dynamics; strong positive feedback between the slip and the friction produces multi-scale chaos. Unfortunately, 3-d continuum problems with strong-rate-weakening friction are numerically intractable. Therefore we (Ahmed Elbanna and I) investigated the much simpler problem of 1-d spring block sliders with strong-rate-weakening-friction. We show that the system produces power-law complexity. That is, the pre-stress evolves into a state that is heterogeneous at all scales. Since the pre-stress and the events are spatially heterogeneous, we must generalize our definition of “strength.” We define “stress-based strength” to be the spatial average of the pre-stress in a failure region, and we define “work-based strength” to be the average work per unit of deformation. We show that these strengths are not the same. Furthermore, we show that the larger the event (or system), the smaller the strength. We show that the strength decreases as a power with the size; the exponent of this relation is related to the dynamic heterogeneity of the system. Since the model is homogeneous, all complexity is dynamic. Earthquakes are so gentle because the Earth is so big. Finally we show a surprising new energy transport equation that reproduces the chaotic behavior of the full numerical simulation. The equation is multi-scale and many orders of magnitude faster than the full numerical system.
© Research Center for Earthquake Hazards.
© Research Center for Earthquake Hazards.
