Present‐day crustal stress field in Greece inferred from regional‐scale damped inversion of earthquake focal mechanisms

Abstract

In this study we utilize regional and teleseismic earthquake moment tensor solutions in order to infer the contemporary crustal stress in the Greek region. We focus on crustal earthquakes and select only solutions with good waveform fits and well‐resolved nodal planes. A data set of 1614 focal mechanisms is used as input to a regional‐scale damped stress inversion algorithm over a grid whose node spacing is 0.35°. Several resolution and sensitivity tests are performed in order to ascertain the robustness of our results. Our findings show that for most of the Greek region the largest principal stress σ1 is vertically oriented and that the minimum principal stress axis σ3 are subhorizontal with a predominant N‐S orientation. In the SW Peloponnese the orientation of σ3 axes rotates clockwise and in SE Aegean counterclockwise. These results are in agreement with the generally accepted model that slab rollback combined with gravitational spreading of the Aegean lithosphere are the main causes of the extension. Transitions between different faulting types in NW Greece or in the Aegean occur within narrow zones in the order of tens of kilometers. A visual comparison of the principal horizontal stress axes and the principal strain axes derived from GPS observations shows good agreement, suggesting that the crust in the Greek region behaves largely in an elastic manner.

Displacement Accumulation and Sampling of Paleoearthquakes on Active Normal Faults of Crete in the Eastern Mediterranean

“…Peloponnese and southern Crete may accommodate up to 85% of the plate-motion (either on the main subduction thrust or on splay-thrust faults) (Howell et al, 2017;Saltogianni et al, 2020). These locked patches are also reflected in the instrumental seismicity catalog where moderate-to-large thrust and strikeslip events are commonly produced in the deeper (>15 km) sections of the crust beneath Crete, and normal-fault focal mechanisms in the overlying upper crust (<15 km) (Kiratzi & Louvari, 2003;Konstantinou et al, 2017). Further, GPS data reveal that the margin-normal component of the relative Eurasian-Africa plate motion decreases from west to east along Crete, with extensional kinematics dominating in eastern Crete (Floyd et al, 2010;Reilinger et al, 2006;Saltogianni et al, 2020).…”

Interpretations of Reservoir‐Induced Seismicity May Not Always Be Valid: The Case of Seismicity during the Impoundment of the Kremasta Dam (Greece, 1965–1966)

“…A second difficulty is that the two shocks have different focal mechanisms (Stein et al, 1982) and belong to different tectonic provinces: an extensional to east and compressional province to the west, separated by a narrow transition zone correlating with the Pindus Thrust ( Fig. 1a-c; Konstantinou et al, 2017). For this reason, the Katouna earthquake has been regarded as an independent earthquake (Anderson and Jackson, 1987;Ambraseys and Jackson, 1990;Baker et al, 1997), that reflected the reactivation of one of the NNW-striking thrusts which control the tectonics of western Greece (Bornovas and Rondogianni-Tsiampaou, 1983).…”

“…(c) The Kremasta reservoir in relation to the epicentre of the 1966 Ms6.2 earthquake (black and white star, after Ambraseys andJackson, 1990 (A &J 1990), derived from macroseismic data). In (b-d) the Pindus Thrust represents a simplified boundary between an extensional terrain to the east and a strike slip/compressional terrain to the west (Bornovas and Rondogianni-Tsiampaou, 1983;Konstantinou et al, 2017). Therianos, 1974).…”

Extrinsic Optical Fiber Pressure Sensor Based on F-P Cavity

“…In-situ stress refers to a natural force that objectively exists in the crustal rock body and is not disturbed by engineering. It causes the crustal rock body to deform, fracture, fold and even earthquake [1][2][3]. With the continuous increase of China's mining, tunnels, water conservancy and hydropower, geothermal energy development, nuclear waste disposal and other projects, such problems as rock burst, roadway deformation, and high slope instability have become increasingly prominent.…”