驱动机制改变对沙堆模型行为特性的影响

Effect of Behavioral Characteristics of Sandpile Model in Time of the Change of Driving Mechanism

慢驱动机制是自组织临界系统(SOC)的基本条件之一,若仅当驱动机制发生改变时,系统的行为特性会呈现何种变化,尚未有人研究.针对这一问题开展了快驱动机制的沙堆模型实验,通过快速倾斜沙堆底板的方式使沙堆从欠临界角快速到达临界角.实验表明,沙堆坡度保持在临界角附近时,落沙量服从幂律分布;随着沙堆坡度逐渐偏离临界角度,落沙量的统计特性将经历对数正态分布-正态分布的转变,不再呈现SOC特性.汶川实震诱发断裂带上盘的崩塌滑坡原型问题是驱动机制改变在自然界中的体现(其隆升速度与滑坡速度之间不存在巨大的时间标度分离).在对汶川地震断裂带上、下盘地区1.5km内的崩塌滑坡规模面积统计分析发现,上盘灾害服从对数正态分布,而下盘不服从对数正态分布.据此,推断汶川地震靠近断裂带上盘附近的崩塌滑坡呈现对数正态分布的规律可能是具普适性意义的现象.

The slowly drive mechanism is one of the essential conditions of self-organized criticality( SOC) system,but it is rarely to study what the behavioral characteristics of the system present in time of the change of driving mechanism. To solve this problem,the fast driven were carried out by rotating floor sandpile model experimentation. By fast tilting the sandpile floor,sandpile is from less critical angle to the critical angle. The result shows when the sandpile angle is near the critical angle,avalanche obeys power-law distribution. With sandpile angle gradually deviates from the critical angle,the statistics of avalanche varies from lognormal distribution to normal distribution,and does not obeys SOC features. The prototypical problem of Wenchuan earthquake inducing the landslide in hanging wall of seismic fault is a reflection of driven mechanism changing in nature( uplift speed and landslides speed have not huge time scale separation). The statistical relationship of the landslide's area of Wenchuan earthquake within1. 5km of hanging wall and footwall shows the hanging wall disaster obeys lognormal distribution,but the footwall disaster does not. Hereby,the landslides in the hanging wall of fault triggered by Wenchuan earthquake obey lognormal distribution,and this phenomenon may have a universal significance.