Performance of the Yangbi M_(S)6.4 earthquake disaster in different geomorphic units in Yunnan

An M_(S)6.4 earthquake occurred in Yangbi,Yunnan province,on May 21,2021.According to related investigations,the macro-epicenter of the earthquake is 6 km northwest of Yangbi County,and the seismogenic structure is the NW-trending Weixi-Qiaohou fault.The earthquake area is located in the hinterland of the Hengduan Mountains in the northwest of Yunnan Province,a region dominated by high and medium-high mountains,with deep canyons and tectonic basins in between.Various geomorphic features are derived from drastic topographic changes and huge geological differences in the earthquake area.There are a variety of buildings in the earthquake-affected zone,including civil and brick-wood structures ones with weak seismic performance,as well as brick-concrete and frame ones with better seismic performance.This paper summarizes and analyzes different characteristics of the earthquake in different geomorphic units through field investigations of different buildings and geological disasters in the affected area.The results show that under the same earthquake intensity,the damage to most buildings(located in slope areas or rooted in weak strata)is amplified by the earthquake.The earthquake has exerted an obvious propagation effect along the direction of the seismogenic structure.Moreover,local ground fissures will aggravate the damage to the buildings even without surface dislocation.Thus,we suggest that attention should be paid to the ground fissures caused by the slope effect.The fissure areas may also be the disaster spot of collapses and landslides in case of a high-magnitude earthquake.

A method for groundwater prospect zonation in data poor areas using remote sensing and GIS:a case study in Kalikavu Panchayath of Malappuram district,Kerala,India

The present study was an attempt to delineate potential groundwater zones in Kalikavu Panchayat of Malappuram district,Kerala,India.The geo-spatial database on geomorphology,landuse,geology,slope and drainage network was generated in a geographic information system(GIS)environment from satellite data,Survey of India topographic sheets and field observations.To understand the movement and occurrence of groundwater,the geology,geomorphology,structural set-up and recharging conditions have to be well understood.In the present study,the potential recharge areas are delineated in terms of geology,geomorphology,land use,slope,drainage pattern,etc.Various thematic data generated were integrated using a heuristic method in the GIS domain to generate maps showing potential groundwater zones.The composite output map scores were reclassified into different zones using a decision rule.The final output map shows different zones of groundwater prospect,viz.,very good(15.57%of the area),good(43.74%),moderate(28.38%)and poor(12.31%).Geomorphic units such as valley plains,valley fills and alluvial terraces were identified as good to excellent prospect zones,while the gently sloping lateritic uplands were identified as good to moderate zones.Steeply sloping hilly terrains underlain by hard rocks were identified as poor groundwater prospect zones.