This work presents a new methodology designed to estimate the slowness vector in large-aperture sparse Ocean Bottom Seismometer (OBS) arrays. The Continuous Wavelet Transform (CWT) is used to convert the original incoherent traces that span a large array, into coherent impulse functions adapted to the array aperture. Subsequently, these impulse functions are beamformed in the frequency domain to estimate the slowness vector. We compare the performance of this new method with that of an alternative solution, based on the fast Short-Term Average/Long-Term Average algorithm and with a method based on the trace envelope, with the ability to derive a very fast detection and slowness vector estimation of seismic signal arrivals. The new array methodology has been applied to data from an OBS deployment with an aperture of 80 km and an interstation-distance of about 40 km, in the vicinity of Cape Saint Vincent (SW Iberia). A set of 17 regional earthquakes with magnitudes 2 < mbLg < 5, has been selected to test the capabilities of detecting and locating regional seismic events with the Cape Saint Vincent OBS Array. We have found that there is a good agreement between the epicentral locations obtained previously by direct search methods and those calculated using the slowness vector estimations resulting from application of the CWT technique. We show that the proposed CWT method can detect seismic signals and estimate the slowness vector from regional earthquakes with high accuracy and robustness under low signal-to-noise ratio conditions. Differences in epicentral distances applying direct search methods and the CWT technique are between 1 km and 21 km with an average value of 12 km. The back-azimuth differences range from 1° to 7° with an average of 1.5° for the P-wave and ranging from 1° to 10° with an average of 3° for the S-wave.

中文翻译：

---

连续小波变换（CWT）的大口径稀疏阵列慢度矢量估计：在海底地震仪中的应用

这项工作提出了一种新方法，旨在估算大口径稀疏海底地震仪（OBS）阵列中的慢度矢量。连续小波变换（CWT）用于将跨越大阵列的原始非相干迹线转换为适合阵列孔径的相干脉冲函数。随后，这些脉冲函数在频域中形成波束，以估计慢度矢量。我们将这种新方法的性能与基于快速短期平均值/长期平均值算法的替代解决方案以及基于跟踪包络的方法的性能进行了比较，该方法具有非常快的检测和慢度的能力地震信号到达的矢量估计。新的阵列方法已应用于开普圣文森特（伊比利亚）附近，孔径为80 km，站间距离约为40 km的OBS部署的数据。选择了一组17次2级<mbLg <5级的区域地震，以测试使用圣文森特OBS阵列探测和定位区域地震事件的能力。我们发现，先前通过直接搜索方法获得的震中位置与使用CWT技术应用产生的慢度矢量估计值计算的震中位置之间有很好的一致性。我们表明，所提出的CWT方法可以在低信噪比条件下以高准确度和鲁棒性检测地震信号并估计区域地震的慢度矢量。使用直接搜索方法和CWT技术的震中距离的差异在1 km和21 km之间，平均值为12 km。反向方位角的差异在P波中为1°至7°，平均为1.5°，而在S波中为1°至10°，平均为3°。