Journal of Tropical Oceanography >
Features of the onshore-offshore seismic data in Southwest Taiwan Strait and some countermeasures for data processing
Received date: 2017-05-12
Request revised date: 2017-07-09
Online published: 2018-04-11
Supported by
Science Foundation of Fujian Earthquake Agency (Y201407)
Natural Science Foundation of China (41674092)
Copyright
In order to study the trend, shape and tectonic setting of the Changle—Nan’ao fault and Binhai (littoral) fault, the Earthquake Administration of Fujian Province expanded seismic sounding into the southwest Taiwan Strait using large volume air-gun arrays and Ocean Bottom Seismometers (OBSs), which formed a relatively complete observation system in conjunction with onshore explosions and portable seismometers. In this paper, we introduce in detail the six profiles collected between 2013 and 2015, including the observation system, acquisition parameters, and data preprocessing. Due to rational choice of shooting parameters and receiver position, a variety of seismic phases, including Pg, PmP, Pn, Sg, and SmS, can be clearly identified in most common receiver gathers of the portable seismometers and OBSs. By multiple shooting the air-gun array at fixed site, we obtained several stacked common shot gathers, of which the signal-to-noise ratios were as high as those acquisition with ton-level explosions. Compared with the data recorded by onshore seismometers, the data recorded by OBSs have a relative low signal-to-noise ratio, which probably means that the seabed in this area has a higher absorption. In light of low velocity and acute variety of deposition thickness in the southwest Taiwan Strait, we transfer the travel times, which were picked up on the common receiver gathers to shot domain, in order to avoid the errors of sediment model, which resulted in pseudo deep structures.
WANG Sun , QIU Xuelin , FANG Weihua , LIU Shanhu , YAO Daoping . Features of the onshore-offshore seismic data in Southwest Taiwan Strait and some countermeasures for data processing[J]. Journal of Tropical Oceanography, 2018 , 37(2) : 92 -99 . DOI: 10.11978/2017054
Fig. 1 Locations of 2D wide-angle reflection/refraction profiles图1 2013—2015年二维广角反射/折射剖面展布图 |
Fig. 2 Layout chart of HX-7 profile图2 HX-7剖面观测系统图 |
Tab. 1 Acquisition parameters of seismic lines表1 地震测线采集参数统计表 |
测线名 | 年度 | 气枪点数 | 气枪点距/m | 炮线长度/km | 吨级爆破/固定气枪点 | OBS数 | 陆上台站数 |
---|---|---|---|---|---|---|---|
HX9 | 2013 | 620 | 100 | 65 | 0 | 21 | 108 |
HX10 | 2014 | 318 | 200 | 65 | 3 | 21 | 110 |
HX6 | 2014 | 352 | 200 | 70 | 1 | 21 | 110 |
HX12 | 2014 | 675 | 300 | 200 | 0 | 18 | 0 |
HX7 | 2015 | 627 | 200 | 125 | 5 | 27 | 112 |
HX13 | 2015 | 1219 | 200 | 245 | 1 | 25 | 0 |
Fig. 3 Seismic record section of OBS27 in HX13. The reduced travel time = (absolute travel time - distance/reduced velocity), and the reduced velocity is 6.0km·s-1, the same below图3 HX13线OBS27共接收点道集记录 |
Fig. 4 Seismic record section of a fixed air gun source (Shihuangfeng reservoir in HX7)图4 HX7线石黄峰水库气枪固定点激发100次叠加记录 |
Fig. 5 Seismic record section of the explosive source (SP101 in HX10)图5 爆炸震源地震记录截面(HX10线SP101) |
Fig. 6 Counts of PmP picks of offshore/onshore seismometer图6 海上/陆上地震仪PmP震相拾取对比 |
Fig. 7 Seismic record section of the air gun source (No. 1073 in HX9)图7 HX9线1073号气枪激发点道集记录 |
Fig. 8 Combined record section of HX9 (merged with PDS-9000, PDS-9033, PDS-9060, PDS-9080 and PDS-9088)图8 HX9线PDS9000、PDS9033、PDS9060、PDS9080、PDS9088拼接记录 |
Fig. 9 Comparison of travel times in common receiver gather and travel times in common source gather图9 接收点域走时和炮域走时集合对比 |
The authors have declared that no competing interests exist.
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