Tectonic deformation in the Santorini volcanic complex (Greece) as inferred by joint analysis of gravity, magnetotelluric and DGPS observations
Tectonic deformation in the Santorini volcanic complex (Greece) as inferred by joint analysis of gravity, magnetotelluric and DGPS observations
复制标题
通过重力、大地电磁和 DGPS 观测的联合分析推断出圣托里尼岛火山群（希腊）的构造变形
DOI：
--
复制
发表时间：
2019
影响因子：
2.8
通讯作者：
E. Lagios
中科院分区：
文献类型：
--
作者：
A. Tzanis;S. Chailas;V. Sakkas;E. Lagios
圣托里尼火山复合体（SVC）的构造活动很难研究，因为它包括一组被火山碎屑沉积物覆盖的小/笨拙形状的岛屿，这些火山碎屑沉积物中的标志物很快被抹去，而地震活动通常不存在。我们解决这个问题，地球物理勘探方法相结合，以评估长期影响的构造变形和时间推移差分GPS直接评估的大小和运动学的现代变形。前者包括3-D重力建模，以调查火山前阿尔卑斯山基底和自然场电磁感应的构造足迹，以映射电导率异常异常的断层流体循环的副现象。我们的分析确定了以下主要构造要素：
跨桑托林分水岭（TSD），一个分段的NNW-SSE右旋走滑断层，将SVC从连接Cape Exomytis、Kammeni Islets和Oia-Therassia Strait的线的侧面分开。它与一个主要的垂直传导带并置，在基底中形成一系列凹陷和坳陷。Columbo断层带（CFZ）是一对平行的NE-SW近垂直正左旋断层，横跨北方SVC并终止于TSD;它可能与流体注入浅地壳有关，但似乎对地壳电导率的影响有限（与TSD相比）。Anhydros断层带（AFZ）通过其在基底上的足迹来检测，作为Athinios-Monolithos线和Fira之间的一组平行的向北倾斜的NE-SW断层。如果它有任何起伏，它是左侧的。它不具有可区分的电特征，也不会对现今的水平变形产生影响。CFZ和AFZ是对立的，形成了一个地堑，包含Kammeni Islets的火山中心。
从Exomytis角到Athinios，沿着破火山口的东侧到Imerovigli，在一个区域的纵向上确定了东西延伸。其中证实的南北向正断层，可能有助于定位的东部破火山口壁。在锡拉西南部观察到NNE-SSW压缩;这可能产生了E-W故障，并导致了南部破火山口壁的局部化。破火山口在基底上的足迹是一个南北向长、西北向东南向短的斜坡：如果东侧和南侧沿着沿着南北向正断层和东西向逆断层坍塌，那么西侧和北侧可能形成类似的形状。现今变形局限于TSD和CFZ：这只能解释为前者是合成的（右旋）Riedel-R剪切，后者是相反的（左旋）Riedel-R′剪切，由N-S σ1和E-W σ3主应力轴产生。因此，预计更广泛地区的NW-SE右行剪切，并通过几条间接证据表明。这种剪切作用的地理范围及其在爱琴海南部区域构造中的作用仍有待于进一步研究的证实和评价。
当代火山中心在TSD与CFZ/AFZ地堑的界面处发展;火山活动似乎受构造控制，SVC受构造而不是火山活动的影响。
Tectonic activity is very difficult to study in the Santorini volcanic complex (SVC) as it comprises a cluster of small/awkwardly shaped islands covered by pyroclastic deposits from which tell-tale markers are swiftly erased, while seismicity is generally absent. We address the problem by combining geophysical exploration methods to evaluate the long-term effects of tectonic deformation and time-lapse differential GPS to directly evaluate the magnitude and kinematics of present-day deformation. The former comprise 3-D gravity modelling to investigate the footprint of tectonics on the pre-volcanic Alpine basement and natural-field EM induction to map conductivity anomalies epiphenomenal to fluid circulation in faults. Our analysis identified the following principal tectonic elements:
The Trans-Santorin Divide (TSD), a segmented NNW–SSE dextral strike-slip fault splitting the SVC sideways of the line joining Cape Exomytis, the Kammeni Islets and the Oia–Therassia Strait. It is collocated with a major vertical conductive zone and forms a series of dents and depressions in the basement. The Columbo Fault Zone (CFZ) is a pair of parallel NE–SW subvertical normal-sinistral faults straddling the northern SVC and terminating against the TSD; it may be associated with fluid injection into the shallow crust but appears to have limited effect on crustal conductivity (compared to TSD). The Anhydros Fault Zone (AFZ) is detected by its footprint on the basement, as a set of parallel northerly dipping NE–SW faults between the Athinios–Monolithos line and Fira. If it has any heave, it is left-lateral. It does not have distinguishable electrical signature and does not contribute to present-day horizontal deformation. The CFZ and AFZ are antithetic and form a graben containing the volcanic centre of Kammeni Islets.
E–W extension was identified lengthwise of a zone stretching from Cape Exomytis to Athinios and along the east flank of the caldera to Imerovigli. N–S normal faulting confirmed therein, may have contributed to the localization of the east caldera wall. NNE–SSW compression was observed at SW Thera; this may have produced E-W failure and contributed to the localization of the south caldera wall. The footprint of the caldera on the basement is a parallelogram with N–S long and WNW–ESE short dimensions: if the east and south flanks collapsed along N–S normal and E–W inverse failures, then the west and north flanks may have formed analogously. Present-day deformation is localized on the TSD and CFZ: this can only be explained if the former is the synthetic (dextral) Riedel-R shear and the latter the antithetic (sinistral) Riedel-R′ shear, generated by N–S σ1 and E–W σ3 principal stress axes. Accordingly, NW–SE right-lateral shearing of the broader area is expected and indicated by several lines of indirect evidence. The geographic extent of this shearing and its role in the regional tectonics of the south Aegean remains to be confirmed and appraised by future research.
Contemporary volcanic centres develop at the interface of the TSD with the CFZ/AFZ graben; volcanism appears to be controlled by tectonics and the SVC to be shaped by tectonic rather than volcanic activity.
影响因子：
5.3
作者：
Hooft, E. E. E.;Heath, B. A.;Warner, M. R.
通讯作者：
Warner, M. R.