Modelling slip distribution of Chirpan-Plovdiv seismic doublet (1928), related to the heterogeneity of the earth crust derived by gravity and magnetic measurements

The April 1928 seismic sequence in the Maritsa River valley of southern Bulgaria, comprising the Chirpan (Mw 6.9) and Plovdiv (Mw 7.1) earthquakes, represents one of the most destructive events in southeastern Europe. Previous studies have constrained the overall fault geometry and kinematics using macroseismic data and geodetic measurements; however, the internal heterogeneity of the rupture remains poorly resolved. Contemporary models indicate that seismic rupture is an inherently heterogeneous process, characterized by localized zones of intense slip (asperities) that influence rupture propagation and energy release. Probabilistic slip models enable the reconstruction of such historical events under conditions of limited data and can be integrated with geological and geophysical information. Gravity and magnetic anomaly data from the Chirpan–Plovdiv region reveal significant lateral heterogeneity in the Earth’s crust, which likely governs the development and termination of rupture processes.1928年4月发生于保加利亚南部马里查河谷的地震序列，涵盖奇尔潘（Mw 6.9）与普罗夫迪夫（Mw 7.1）两次地震，是东南欧地区破坏性最强的地震事件之一。既往研究借助宏观地震数据与大地测量手段，限定了该区域的整体断层几何形态与运动学特征，但破裂过程的内部非均质性仍未得到充分解析。当前地震学模型表明，地震破裂本质上是一个内在的非均质性过程，以局部强滑动区（凹凸体，asperities）为典型特征，这类区域会对破裂传播与能量释放产生影响。概率滑动模型可在数据有限的条件下，重建这类历史地震事件，并可与地质、地球物理信息进行整合。针对奇尔潘-普罗夫迪夫区域的重力与磁异常数据研究显示，地壳存在显著的横向非均质性，这可能主导了破裂过程的发育与终止。