The earthquake Frequency Magnitude Distribution (FMD) or b values have been meticulously used in the last two decades as a deterministic earthquake precursor or indicator, in earthquake forecasting or probabilistic seismic hazard assessment studies, in a variety of tectonic and stress regimes. In the present study, temporal fluctuations of b values were analysed by means of 185 well located (Mw ≥ 5) earthquakes, in the region of Andaman and Nicobar Islands (N10° to 14°) for a time period of ∼100 years (1918 to 2018). Variation in b value rates before and after the 2004 great Sumatra-Andaman earthquake (Mw 9.3) was analysed, preceded by a comprehensive geodynamic and seismotectonic- crustal deformation overview along the Andaman trench section. The analysis suggest a precursory drop in b values from 1.05 ± 0.05 (1918 to 2004) to 0.90 ± 0.05 post 2004 earthquake (2004 to 2018) reflecting a greater slip deficit and strain localization, that exceeds considerably the pattern of energy release in this region. Further, the region of Andaman and Nicobar Islands have witnessed a poor slip distribution (on-fault reactivation) from the great earthquakes that nucleated near the Sumatra segment, and have ruptured few large earthquakes, with no accounts of great earthquake (>Mw 8) during the last century. This emphasizes that, strain accumulation has been concentrated over a long period of time, and can contribute a destructive deformation event in near future.

在过去的二十年中，在各种构造和应力情况下，地震频率幅值分布（FMD）或b值一直被用作确定性地震前兆或指示物，用于地震预测或概率性地震危险性评估研究中。在本研究中，通过安达曼和尼科巴群岛地区（N10°至14°）持续时间约100年（1918年）的185处地点（Mw≥5）地震分析了b值的时间波动。至2018年）。分析了2004年苏门答腊-安达曼大地震（Mw 9.3）前后b值的变化，然后对安达曼海沟段的地球动力学和地震构造地壳进行了全面的概述。分析表明，b值从1.05±0.05（1918年至2004年）下降到0.90±0。2004年5月后的地震（2004年至2018年）反映出更大的滑移赤字和应变局部化，大大超出了该区域的能量释放模式。此外，安达曼和尼科巴群岛地区经历了苏门答腊段附近成核的大地震，滑移分布不佳（断层复活），并且破裂了几次大地震，没有大地震的记载（> Mw 8）在上个世纪。这强调了，应变积累已长期集中，并可能在不久的将来造成破坏性变形事件。在安达曼和尼科巴群岛地区，苏门答腊段附近发生了大地震，滑移分布不佳（断层复活），并且在这次地震中几乎没有破裂大地震，也没有大地震（> Mw 8）的记录。上世纪。这强调了，应变积累已长期集中，并可能在不久的将来促成破坏性变形事件。在安达曼和尼科巴群岛地区，苏门答腊段附近发生了大地震，滑移分布不佳（断层复活），并且在这次地震中几乎没有破裂大地震，也没有大地震（> Mw 8）的记录。上世纪。这强调了，应变积累已长期集中，并可能在不久的将来造成破坏性变形事件。