Oceanographic, seismographic and hydrographic surveys were completed after each nuclear blast. Following the relief efforts, 19 seismographic stations were installed to monitor seismic activities. Bentov's invention was a seismographic device to record the heartbeat, in particular the aorta's reverberations. By the 13th century, seismographic devices existed in the Maragheh observatory in Persia. The earthquake was recorded by 110 seismographic stations around the world. The BMKG issued a tsunami warning based on seismographic data. In addition, occasional reconnaissance flights, seismographic monitoring, and infrequent visits to the volcano occur. Here, there were a plethora of blast, pressure and seismographic gauges. They started by providing service to a seismographic group working in the wetlands of Louisiana. It features three large windows that allow visitors to view the seismographic equipment within. The East Germany authorities eventually used seismographic and acoustic equipment to detect the practice. Mount St. Michael soon gained international acknowledgement as an important seismographic center. Seismographic crews were again present in the area in the early 1980s. Currently the seismographic network has a registration system analog and one digital. Currently, the seismographic network has an analog and a digital registration system.