Abstract

Based on analysis of remote sensing images, geomorphological distortion, geology, and tectonics, the authors defined neotectonic and modem geodynamic characteristics of Hướng Hóa - Đăkrông area, Quảng Trị province. There is a structural schema of its regional neotectonic including structural blocks and faults. These blocks are Hướng Lập, Hướng Son, Ba Lòng, Triệu Nguyên, Húc Nghi, A Ngô, Hướng Lộc - A Vao and Hướng Phùng. The tectonic fault zones are Đăkrông - Huế, Hướng Hóa - A Lưới, Cam Lộ River, Quảng Trị River, Mò ộ -Tân Lập, and Tà Long - A Vao, in which Hướng Hóa - A Lưới and Đăkrông - Huế fault zones play an important role in forming of the structural schema. Most of NW-SH faults as the Cam LỘ River, Hướng Hóa - A Lưới, Đăkrông-Huế, and Quảng Trị River faults are in northeast with a dip angle of 60-80°. There were two phases of neotectonic geodynamic setting in the area: the first was Early Miocene-Pliocene phase in dynamic compression with sub-latitude direction, the NW- SE faults are Cam Lộ River, Quảng Trị River, Đăkrông - Huế and Hướng Hóa - A Lưới... left and normal-left strike-slip faults; NE-SW Mò Ô - Tân Lập faults are right strike-slip and others submeridian faults were compressed activities. The second phase occurred in Pliocene-Quaternary with compressed activities in submeridian direction, the NW-SE faults were normal right strike-slip faults; NE-SW faults were left strike-slip faults; the subparallel faults were reserved faults, the submeridial faults were normal faults. The geodynamic processes happened along active fault zones in the region including: basalt eruption activity during Pliocene-Quaternary, cracked soils, earthquakes, hot spring outcrops, and geothermal sources.