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Rainfall event is a stochastic process, so to explain and analyze this processes the probability theory and frequency analysisare used. There are four types of probability distributions.They are normal, log normal, log Pearson III and Gumbel. To find the best probabilities distribution, it will used goodness of fit test. The tests consist of chi-square and smirnov-kolmogorov. Results of the chi-square test for normal distribution, log normal and log Pearson III was 0.200, while for the Gumbel distribution was 2.333. Results of Smirnov Kolmogorov test for normal distribution D = 0.1554, log-normal distribution D = 0.1103, log Pearson III distribution D = 0.1177 and Gumbel distribution D = 0.095. All of the distribution can be accepted with a confidence level of 95%, but the best distribution is log normal distribution.Kejadian hujan merupakan proses stokastik, sehingga untuk keperluan analisa dan menjelaskan proses stokastik tersebut digunakan teori probabilitas dan analisa frekuensi. Terdapat empat jenis distribusi probabilitas yaitu distribusi normal, log normal, log pearson III dan gumbel. Untuk mencari distribusi probabilitas terbaik maka akan digunakan pengujian metode goodness of fit test. Pengujian tersebut meliputi uji chi-kuadrat dan uji smirnov kolmogorov. Hasil pengujian chi kuadrat untuk distribusi normal, log normal dan log pearson III adalah 0.200, sedangkan untuk distribusi gumbel 2.333. Hasil pengujian smirnov kolmogorov untuk distribusi normal dengan nilai D = 0.1554, distribusi log normal dengan nilai D = 0.1103, distribusi log pearson III dengan nilai D = 0.1177 dan distribusi gumbel dengan nilai D = 0.095. Seluruh distribusi dapat diterima dengan tingkat kepercayaan 95%, tetapi distribusi terbaik adalah distribusi log normal.

In the last five years, landslide occurred many times in this area. The worst landslide was in 2014, which destroyed many houses and infrastructure such as road, water supply utilities and electricity. This study proposed an identification of landslide method by using of geo electricity as subsurface investigation of landslide. This study aims to identify the type of landslide and slip surface potential by using emergence of 2D spatial imaging. The application of geophysical has not been used as a result of landslide identification. The well-known argument state that geophysical is the only way to make images on the type and rock by using resistivity. The geological and soil physical properties required by engineers to analyse landslide potential are not well presented. As a consequence, the solution of soil reinforcement on landslide prone area to minimize the risk is presented as an engineering judgment of problem solving. Therefore, this paper discusses about soil properties and imaging to identify the area affected by future landslide. By using a multi-electrode electrical array, the 2D geophysical imaging was used to investigate the complex structure of soil stratigraphy and geological properties. The results showed that the area of the study was shown as a stable area with andesite intrusion. In addition, some areas were suspected as landslide prone area which was indicated resources by saturated clay of soil beneath.

The discontinuity of geological structure on tuff layer of rock slopes in Manado triggered a phenomenon of rock slope instability. Mohr-Coulomb criterion which is commonly used as a method of analysis is not suitable to solve the slope stability problem because this criterion does not consider the condition of the geological structure as one of its factors. This paper analyzed the rock slope stability by accommodate the condition of the geological structure using Hoek-Brown criterion. Geological structure effect in Hoek-Brown criterion was realized in the form of GSI (Geological strength index). Poor geological structure will reduce GSI. In this paper, GSI of tuff has been determined by discontinuities of mapping and back analysis. The results from discontinuities mapping revealed that the rock structures were very blocky to blocky and surface conditions were very poor to poor. GSI value ranges between 20-30. From back analysis with shear strength reduction, GSI value was 20 and UCS value was 230 kN. The results are quite close with the field observation.