LISBON—Volcano-tectonic tremors, which indicate the movement of magma, were recorded on the earthquake-hit mid-Atlantic Azores island of Sao Jorge for the first time since a worrying seismic crisis began more than two weeks ago, authorities said on Wednesday. The lush green volcanic island, in Portugal’s Azores archipelago, has been hit by 27,626 small tremors and there are fears the activity could herald an eruption or a powerful earthquake. Fatima Viveiros, from the region’s CIVISA seismo-volcanic surveillance centre, said volcano-tectonic earthquakes, also known as hybrid, happen when there is a “fusion” of high-frequency tectonic tremors with low-frequency volcanic ones. “[It] suggests the movement of fluids at depth,” Viveiros explained, adding that more earthquakes of that kind were expected. “These signals show what is to be expected in active volcanic systems.” The volcanic alert is at Level 4 on a five-step scale, meaning there is a “real possibility” the volcano could erupt …