50.世界の特殊な地役地域の活動について : その2 BurmaからJava島まで

Seismicity in Burma was studied with relation to the seismicity along Andaman, Nicobar, Greater Sunda Islands and Java as a continuation of the same seismic zone. Foci distributions of the earthquakes versus depth in the various regions from Northern Burma down to Java Island were found to be expressed by the same curve, which indicates that the continental earthquakes in Burma have the same source of generation as that of oceanic ones belonging to the trench-island arc system. Energy released by the earthquakes in Burma, however, has quite a unique action, that is, a large amount of energy has been released in the upper mantle between the depth range of 50km and 200km. Special events which follow one or two other events with close relationship to the first one both in space and time have taken place in the oceanic belt. There are no such events in Burma. Earthquakes deeper than 550km have been generating only in part beyond latitude 110°E. Extension of foci plane appears to have a close relation with the formation of trench. It was discovered that many deep earthquakes in Java Sea have the tendency to take place at the same spots with various time intervals. Distributions of seismological stations, the data of which have often been available to U.S. Coast and Geodetic Survey for foci determination, were examined. Services from the eastern stations were found to be poor at least for detecting the smaller events.|Burma北方の褶曲の状態は,前篇で取扱つたHindu Kush周辺のそれとよく似ているにかかわらず,ここでの上部マントル地震には,前篇でのべたようなかたまりはみられず.かえつてBurma西部の国境沿いに南北に走る弓形の山脈に沿つて起こつており,明らかに南のSunda-Nicobar-Andaman諸列島沿いに北上する島弧系の地震帯が,そのまま大陸内に廷長されたものと見なせる.このことが,震源分布をしらべた結果一層はつきりした