Contrasting deformation styles along an active thrust belt front - the external Dinarides and Hellenides

巴尔干半岛上的Dinarides-Hellenides褶皱冲断带是一个罕见的大陆活动俯冲的例子。我们建议在克罗地亚南部、黑山和阿尔巴尼亚北部之间的一个瞬态运动学区域研究其活动构造。该地区有几个异常特征需要澄清：(a)地震矩释放向北减弱；(b)大陆岩石圈板块向北消失；(c)与俯冲回滚有关的同碰撞伸展向北结束。该研究区域曾发生过许多历史上的地震，以及欧洲仪器记录的最强地震之一（1979年黑山，里氏7.1级）。GPS研究表明，亚德里亚和欧亚大陆之间的辐合速度为每年4-5毫米，主要位于外部冲断带内。相比之下，长期趋同率仍然不受限制。我们的目标是用两方面的方法来描述这种瞬态运动行为的结构基础：(1)垂直于造山带的斯库塔里-佩克断裂两侧的两个区域样带的平衡横截面划分了向北的同碰撞伸展，将允许量化整个新生代地壳缩短以及斯库塔里-佩克断裂南部样带的回滚触发伸展的贡献。(2)目前主要通过构造地貌学和古地震学研究来识别活动构造。通过对受河流切割和褶皱生长影响的第四纪河流阶地进行定年，将重点放在量化邻近沿海地区的地表隆升和活动褶皱速率上。结合对活动断层几何形状的限制，这将允许在10-100 kyr的时间尺度上估计断层滑动率。这些滑动率估计将提供许多地震周期的平均值，而gps导出的收敛率仅适用于过去1-2年，即自1979年事件以来的地震平静期。长期和短期滑动率的比较可以潜在地突出锁定断层，因此对评估地震危险性具有相关性。我们的研究也将有助于更好地理解以低板块收敛率为特征的地区的大陆俯冲和逆冲带的传播。

The fold-and-thrust belt of the Dinarides-Hellenides on the Balkan Peninsula is a rare example of active continental subduction. We propose to study its active tectonics in an area of transient kinematics between southern Croatia, Montenegro and northern Albania. Several anomalous features characterize this area and need clarification: (a) northward-diminishing seismic moment release, (b) northward disappearance of a continental lithospheric slab and (c) northward end of syn-collisional extension related to subduction rollback. The study area hosted numerous historical earthquakes as well as one of the strongest instrumentally recorded earthquakes in Europe (Montenegro 1979, MW 7.1). GPS studies indicate convergence between Adria and Eurasia at rates of 4-5 mm yr-1, largely accommodated within the external thrust belt. Long-term convergence rates, by contrast, remain unconstrained. We aim to characterize the structural basis of this transient kinematic behaviour in a two-fold approach: (1) Balanced cross sections in two regional transects on either sides of the orogen-perpendicular Skutari-Pec Fault, which delimits syn-collisional extension to the north, will allow quantifying the overall Cenozoic crustal shortening as well as the contribution of rollback-triggered extension in the transect south of the Skutari-Pec Fault. (2) Presently active structures will be identified by tectonic geomorphological and paleoseismological studies. Emphasis will be given to quantifying rates of surface uplift and active folding in the adjacent coastal areas by dating Quaternary aggradational river terraces affected by river incision and fold growth. In combination with constraints on geometries of active faults, this will allow estimating fault slip rates on a 10-100 kyr time scale. These slip rate estimates will provide average values across many seismic cycles compared to GPS-derived convergence rates that are valid only for the last 1-2 decades, i.e., a seismically quiet period since the 1979 event. The comparison of long-term and short-term slip rates can potentially highlight locked faults and is hence of relevance for assessing the seismic hazard. Our study will also contribute towards a better understanding of continental subduction and thrust belt propagation in areas characterized by low plate convergence rates.