SUMMARY

Interpretation of the Mantle movement and lithosphere stress field
of the South East Asia according to the p wave tomography

Cao Đnh Triều, Đặng Thanh Hải, L Vn Dũng, Cao Đnh Trọng

 

In this paper, the authors expound the mantle movement and lithosphere stress pattern of the South East Asia according to the p wave tomography. The obtained results have shown that: The surrounded subduction zones of the South East Asia have been characteristic as the vertical mantle fluid in the upper mantle, transitional and layer 1. The earthquake concurrency in this zone are high frequency and rather strong in comparison ones in the intra-plate region. This boundary zone characterizes by the relative pinching out of the lithosphere (with the depth from 70 to 110 km) and can be divided into the following blocks: 1/ Myanmar (Indo-Burma - 80-100 km); 2/ Nicobar (Andaman Sea - 70-75 km); 3/ Sumatra (75-95 km); 4/ Java (80-95 km); 5/ Timor (95- 110km); 6/ Halmahera (95-105 km); 7/ Sulu Sea (90-110 km); 8/ Sulawesi (70-90 km); 9/ Philippines (85-110 km); 10/ Manila (95-105 km); 11/ Taiwan (80-90 km); 12/ Bataan (80-90 km); The Hai Nam - Natuna deep fault zone plays role as the separation line to devise the mantle of the South East Asia into two parts: east and west parts. In the east part of the South East Asia mantle, the p wave velocities are changing sharply in the vertical. Meanwhile, in the west part, the p wave velocities are changeable chaotically. The South East Asia intraplate is characterized by very complicated structures of the lithosphere and can be divided into the following blocks: 1/ Sino- Burma (90-100 km); 2/ Shan Thai (95-105 km); 3/ Battani (85-95 km); 4/ Indochina (80-105 km); 5/ Malaysia (85-95 km); 6/ Natuna (100-105 km); 7/ South China - North Việt Nam (85-100 km); 8/ Hong Sa (75-85 km); 9/ Centre of Việt Nam East Sea (65- 80 km); 10/ Trường Sa (90-110 km); 11/ North Kalimantan (95-100 km); 12/ Kalimantan (90-95 km); 13/ Barito (85-90 km); 14/ Banda (65-90 km); 15/ Sulu (Sulu Sea and Sulawesi Sea, 60-90 km). The mantle flows are the reason of the South East Asia lithosphere horizontal movement. The maximum stress axis (ơi) has the direction from north to south in the north part of the South East Asia. This direction has traieds and have north-east direction in the centure of Việt Nam East Sea. The smrounded subduction zones of the South East Asia are laying under the state of compression (Manila trench, Philippine trench, Sumatra-Java-Timor trench) and shearing (Saigang fault zone).