Development of hybrid simulator with physical and statistical models for landform change

本研究项目地形模拟器的主要目的是：(1)在假定地震引起的大地大震动诱发大规模滑坡，且滑坡频率与地震活动频率相关的情况下，模拟河流山段的陆面震级-频率关系；(2)在河流沿线包含满足质量恒定定律的物理关系。为了达到这些目的，我们进行了以下三个主题：(a)讨论了DEM（数字高程模型）分辨率与坡度、拉普拉斯等地貌学结果的关系，并表明至少需要25m或更详细的DEM来模拟河流沿线的地形变化。(b)计算了日本地震构造省的震级-频率关系，并讨论了如何将这种关系纳入地形模拟器的定量评价。(c)利用Borland c++ Builder开发运行在Microsoft-Windows上的地形模拟器编程代码，能够读取初始地形，读取漫射系数、后退系数、剥蚀率、隆起率、基底高度等参数，并将结果可视化。利用该代码对日本中部赤石山脉的地形变化进行了模拟，结果显示地形剖面和坡度直方图中出现了以往模拟器无法实现的陡坡。

The main purposes of the landform simulator in this research project are (1)to model the magnitude-frequency relationship of landsides in the mountain section of river streams under the assumption that large scale of landslides are induced by the large ground shaking caused by the earthquakes and the frequency is related to that of seisimicity, and (2)to include physical relationship satisfying the law of constancy of mass along the river stream. We conducted following three subjects to achieve these purposes :(a)Discuss the relationship between DEM (digital elevation model) resolution and geomorphometric results such as slope and laplacian and show that at least 25m or more detailed DEM is needed to simulate the landform change along river stream.(b)Calculate seismic magnitude-frequency relationship in Japanese seismotectonic provinces and discuss the quantitative evaluation how to include this relationship into landform simulator.(c)Develop the landform simulator programming code running on Microsoft-Windows by the use of the Borland C++ Builder, which are capable of reading initial topography, reading parameters such as diffuse coefficient, retreat coefficient, denudation rate, uplift rate and base altitude, and visualize results. We simulate the landform change in the Akaishi mountains central Japan by using this code and the result show the appearance of steep scarp in cross section of landforms and slope histogram, which could not conduct previous simulators.