Comparison of crustal and upper mantle heterogeneity in different time periods: Indonesian subduction zone to northern Australia
Weijia Sun1,2, Li-Yun Fu1,2, B. L. N. Kennett1,2
Key Laboratory of the Earth’s Deep Interior, Institute of Geology and Geophysics, Chinese Academy of Science, Beijing 10029, ChinaKey Laboratory of the Earth’s Deep Interior, Institute of Geology and Geophysics, Chinese Academy of Science, Beijing 10029, China Research School of Earth Sciences, The Australian National Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia
Comparison of crustal and upper mantle heterogeneity in different time periods: Indonesian subduction zone to northern Australia
Weijia Sun1,2, Li-Yun Fu1,2, B. L. N. Kennett1,2
1 Key Laboratory of the Earth’s Deep Interior, Institute of Geology and Geophysics, Chinese Academy of Science, Beijing 10029, China 2 Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia
摘要Earthquake events from the Indonesian subduction zone recorded in northern Australia show a long and high-frequency coda associated with both P and S waves. Regional events recorded by Warramunga array in northern Australia can separate out wave propagation through the mantle by focusing on the coherent signal across the medium-aperture array. Most of the incoherent wave components result from structures in the vicinity of the array with small-scale lengths of 1–2 km or smaller. The coherent phases with relatively rapid changes in waveforms are associated with the scattering of seismic waves by crustal and mantle heterogeneity, but in some case can be related to structural effects near the source. As the depth of the source increases, the coherent portion of the seismic wavefield tends to become much simpler, which suggests that the heterogeneity tends to weaken at depth with larger-scale length. We compare the coherent signal features of earthquakes from the Indonesian subduction zone that have occurred in recent years with those in the early 1980s, first studied by Kennett (Phys Earth Planet Inter 47: 319–332, 1987). The general characteristics of the coherent signal variation with depth in recent years are the same as those observed in 1980s, but the variations are larger. This change suggests a stringer variation in heterogeneity with depth than before, which may bear important information about the dynamic processes and evolution of the crust and upper mantle.
Abstract：Earthquake events from the Indonesian subduction zone recorded in northern Australia show a long and high-frequency coda associated with both P and S waves. Regional events recorded by Warramunga array in northern Australia can separate out wave propagation through the mantle by focusing on the coherent signal across the medium-aperture array. Most of the incoherent wave components result from structures in the vicinity of the array with small-scale lengths of 1–2 km or smaller. The coherent phases with relatively rapid changes in waveforms are associated with the scattering of seismic waves by crustal and mantle heterogeneity, but in some case can be related to structural effects near the source. As the depth of the source increases, the coherent portion of the seismic wavefield tends to become much simpler, which suggests that the heterogeneity tends to weaken at depth with larger-scale length. We compare the coherent signal features of earthquakes from the Indonesian subduction zone that have occurred in recent years with those in the early 1980s, first studied by Kennett (Phys Earth Planet Inter 47: 319–332, 1987). The general characteristics of the coherent signal variation with depth in recent years are the same as those observed in 1980s, but the variations are larger. This change suggests a stringer variation in heterogeneity with depth than before, which may bear important information about the dynamic processes and evolution of the crust and upper mantle.
基金资助:the National Natural Science Foundation of China (Grant Nos. 40925013, 41104079 and 41130418)
通讯作者:
Weijia Sun
E-mail: swj@mail.iggcas.ac.cn
引用本文:
Weijia Sun, Li-Yun Fu, B. L. N. Kennett. Comparison of crustal and upper mantle heterogeneity in different time periods: Indonesian subduction zone to northern Australia[J]. 《地震学报》英文版, 2014, 27(1): 47-55.
Weijia Sun, Li-Yun Fu, B. L. N. Kennett. Comparison of crustal and upper mantle heterogeneity in different time periods: Indonesian subduction zone to northern Australia. Earthquake Science, 2014, 27(1): 47-55.
