The research team Earthquake and Avalanche Study Geological Engineering GMU recommends the need created a potential hazard zone mapping earthquake and landslide in West Sumatra (West Sumatra). This is felt very helpful in saving more victims early and support the improvement of spatial and regional development in the reconstruction process forward. "Map of the earthquake and landslide hazards is needed as a landing and spatial refinement of new building regulations in the reconstruction phase, as well as ever conducted in the province of Yogyakarta and Bantul regency," said Chairman Tim Earthquake and Avalanche Study Geological Engineering UGM, Prof.. Dr. Dwikorita Karnawati, Thursday (8 / 10), in Room Parahita Stana, UGM Headquarters.
According Dwikorita, that is not less important than the observations about the geological conditions in the region after the earthquake in Padang, Pariaman, Solok Padang Panjang to glide avalanche is possible aftershocks are still potentially occur if triggered by heavy rains or aftershocks. The observation was also conducted to assess the geological conditions that affect the level of building damage and soil erosion due to the earthquake. From the results of observations and measurements in the field, it is known that the region affected by the earthquake in West Sumatra on September 30 and can be divided into two main areas, namely, alluvial plains and hills area hard.
Includes alluvial plains to Padang Pariaman City, which suffered much damage to buildings due to earthquake shocks. This region is composed of sediments that are loose in the form of clay, clay pasiran, and sand off kerikilan because of the nature of the soil grains making up the alluvial plain.
When an earthquake, earthquake vibration wave propagation complications into the surface which is swung, both the vertical and horizontal, which ultimately resulted in damage and the fall of the building.
"Most of the buildings that collapsed or side tend toward the northwest-southeast, which leads to the earthquake epicenter is located at the relative positions northwest of Padang city," he said.
Unlike the impact of the earthquake in Yogyakarta, said Dwikorita, the damage that occurred on alluvial plains in the Valley do not show a specific pattern of distribution is controlled by soil conditions or geological conditions, it seemed more controlled by the state building construction.
Meanwhile, hard hills region, which includes the Barisan Hills area of Padang Panjang to Solok, many experienced landslides in the earthquake. According Dwikorita, the hills are composed of volcanic igneous and metamorphic rocks are formed by the hills of active faults are known by the name semangko fault.
"In the fault zone rocks making up these hills also mutilated by the cracks of rocks and are fragile. Consequently, when shaken by earthquakes, many occur debris, fallen, and rock slides on hillsides Barisan, especially those passed by fault lines, "he explained.
Several points of land slides occurred had amassed more than 100 people in two villages, namely Hamlet and Lubuk Kapalo Koto village of Lawe Cumanak, Nagari Tandikek, Patamuan District, Padang Pariaman. Rock slope landslides is estimated slopes in the fault lines. Slope ranges from 30 to 40 degrees.
"The condition of the soil in the fault zone is very fragile and still has the potential for landslides again when hit by an earthquake, or washed by heavy rains that this zone is recommended to be closed during rain to avoid casualties if an aftershock aftershocks or landslides occur," he suggested.
Another landslide locations to watch, go Dwikorita, is on a bluff Malalak roads leading to Bukit Tinggi, which is composed of andesite igneous and volcanic rock terutup by Tuf pumisan form, which has decayed into a pasiran clay is very porus and water escape . The slope of this slope ranges from 40o to 60o. Due to steep slopes and fragile soil conditions, when an earthquake occurs, launch the ground with blocks of rock occurred. Zones that experienced glide along the ground reaches 2 km. Glide has also resulted in some roads closed. (KU, 8-10-2009)
