Interpretation
of the Mantle movement and lithosphere stress field
of the South East Asia according to the p wave tomography
Cao Đ́nh Triều, Đặng Thanh Hải, Lê Văn Dũng,
Cao Đ́nh 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/ Hoàng 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).