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Teleseismic P waves at the AlpArray seismic network: wave fronts, absolute travel times and travel-time residuals
Solid Earth ( IF 3.4 ) Pub Date : 2021-07-20 , DOI: 10.5194/se-12-1635-2021
Marcel Paffrath , Wolfgang Friederich ,

We present an extensive dataset of highly accurate absolute travel times and travel-time residuals of teleseismic P waves recorded by the AlpArray Seismic Network and complementary field experiments in the years from 2015 to 2019. The dataset is intended to serve as the basis for teleseismic travel-time tomography of the upper mantle below the greater Alpine region. In addition, the data may be used as constraints in full-waveform inversion of AlpArray recordings. The dataset comprises about 170 000 onsets derived from records filtered to an upper-corner frequency of 0.5 Hz and 214 000 onsets from records filtered to an upper-corner frequency of 0.1 Hz. The high accuracy of absolute and residual travel times was obtained by applying a specially designed combination of automatic picking, waveform cross-correlation and beamforming. Taking travel-time data for individual events, we are able to visualise in detail the wave fronts of teleseismic P waves as they propagate across AlpArray. Variations of distances between isochrons indicate structural perturbations in the mantle below. Travel-time residuals for individual events exhibit spatially coherent patterns that prove to be stable if events of similar epicentral distance and azimuth are considered. When residuals for all available events are stacked, conspicuous areas of negative residuals emerge that indicate the lateral location of subducting slabs beneath the Apennines and the western, central and eastern Alps. Stacking residuals for events from 90 wide azimuthal sectors results in lateral distributions of negative and positive residuals that are generally consistent but differ in detail due to the differing direction of illumination of mantle structures by the incident P waves. Uncertainties of travel-time residuals are estimated from the peak width of the cross-correlation function and its maximum value. The median uncertainty is 0.15 s at 0.5 Hz and 0.18 s at 0.1 Hz, which is more than 10 times lower than the typical travel-time residuals of up to ±2 s. Uncertainties display a regional dependence caused by quality differences between temporary and permanent stations as well as site-specific noise conditions.

中文翻译:

AlpArray 地震台网的远震 P 波:波前、绝对走时和走时残差

我们提供了一个广泛的数据集,其中包含由 AlpArray 地震网络记录的远震 P 波的高精度绝对走时和走时残差以及 2015 年至 2019 年的补充现场实验。该数据集旨在作为远震旅行的基础-大阿尔卑斯地区下方上地幔的时间断层扫描。此外,该数据可用作 AlpArray 记录全波形反演的约束条件。该数据集包含大约 170 000 个起始点,这些起始点来自过滤到 0.5 Hz 上角频率的记录和 214 000 个起始点,这些起始点来自过滤到 0.1 Hz 上角频率的记录。通过应用专门设计的自动拾取、波形互相关和波束成形的组合,获得了绝对和剩余旅行时间的高精度。获取单个事件的走时数据,我们能够详细地可视化远震 P 波在 AlpArray 上传播时的波前。等时线之间距离的变化表明下方地幔中的结构扰动。单个事件的旅行时间残差表现出空间连贯的模式,如果考虑类似震中距离和方位角的事件,这些模式证明是稳定的。当所有可用事件的残差叠加时,显着的负残差区域出现,表明亚平宁山脉和西部、中部和东部阿尔卑斯山下方俯冲板块的横向位置。90 事件的堆积残差 等时线之间距离的变化表明下方地幔中的结构扰动。单个事件的旅行时间残差表现出空间连贯的模式,如果考虑类似震中距离和方位角的事件,这些模式证明是稳定的。当所有可用事件的残差叠加时,显着的负残差区域出现,表明亚平宁山脉和西部、中部和东部阿尔卑斯山下方俯冲板块的横向位置。90 事件的堆积残差 等时线之间距离的变化表明下方地幔中的结构扰动。单个事件的旅行时间残差表现出空间连贯的模式,如果考虑类似震中距离和方位角的事件,这些模式证明是稳定的。当所有可用事件的残差叠加时,显着的负残差区域出现,表明亚平宁山脉和西部、中部和东部阿尔卑斯山下方俯冲板块的横向位置。90 事件的堆积残差 出现了显着的负残差区域,表明亚平宁山脉和西部、中部和东部阿尔卑斯山下方俯冲板块的横向位置。90 事件的堆积残差 出现了显着的负残差区域,表明亚平宁山脉和西部、中部和东部阿尔卑斯山下方俯冲板块的横向位置。90 事件的堆积残差宽的方位角扇区导致负残差和正残差的横向分布,这些分布通常是一致的,但由于入射 P 波对地幔结构的照射方向不同,因此在细节上有所不同。根据互相关函数的峰宽及其最大值估计旅行时间残差的不确定性。中值不确定性在 0.5 Hz 时为 0.15 s,在 0.1 Hz 时为 0.18 s,比典型的高达±2  s 的走时残差低 10 多倍。不确定性表现出由临时站和永久站之间的质量差异以及特定地点的噪声条件引起的区域依赖性。
更新日期:2021-07-20
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