Pockmarks consists of depressions on the seafloor and are often considered to originate from fluid escape activities. In this study, we report 125 pockmarks near the Andu Seamount in the southern margin of the South China Sea (SCS) and preliminarily investigate their genesis based on multi-beam bathymetry and multichannel seismic reflection data. Most of them are giant and mega pockmarks and display circular, elliptical, elongated, crescent, comet and irregular shapes on a plan-view. The mapped pockmarks cover a total surface of 291.354 km². Most of them occur in strings or clusters, while some are isolated. The filled volume of pockmark is calculated for the first time in this region, which may have significant implications for sedimentary process. Beneath most of the pockmarks, high-angle faults, high-amplitude reflections, filled-up structures and other fluid escape features are imaged on seismic sections. The structural settings, especially the fault systems, may control the genesis and development of pockmarks in this area. We also speculate that seabed gradients may contribute to generation of crescent pockmarks. According to seismic sections, sediment types and morphological analysis, we finally proposed that the genesis of these pockmarks may mainly be triggered by gas escape activities in the study area. This work may have important implications for the gas exploration in the Nansha Region, southern South China Sea.

中文翻译：

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南沙地区（南海）安度海山附近的巨型和巨型麻点的形态和成因的初步研究

麻纹由海底的凹陷组成，通常被认为是由流体逸出活动引起的。在这项研究中，我们报告了南海（SCS）南缘安杜海山附近的125个麻点，并根据多波束测深法和多通道地震反射数据初步研究了它们的成因。它们大多数是巨大的和巨大的麻点，并且在平面图上显示圆形，椭圆形，细长，新月形，彗星和不规则形状。映射的麻点覆盖整个表面291.354 km ²。它们大多数以字符串或簇的形式出现，而有些则是孤立的。在该区域首次计算了麻子的填充量，这可能对沉积过程有重要影响。在大多数麻点之下，高角度断层，高振幅反射，填满的结构和其他流体逸出特征都在地震剖面上成像。结构设置，尤其是断层系统，可能会控制该区域麻子的产生和发展。我们还推测，海床梯度可能有助于新月形痘痕的产生。根据地震剖面，沉积物类型和形态分析，我们最后提出这些麻点的成因可能主要是由研究区的瓦斯逸出活动触发的。