Question

In 1936, Danish seismologist Inge Lehmann published a groundbreaking paper titled P' in which she proposed that Earth possesses a solid inner core distinct from its liquid outer core. At the time, geophysicists operated under the two-layer mantle-core model developed by Richard Dixon Oldham in 1906, which posited a single uniform liquid core. Under Oldham's model, seismic compressional waves—known as P-waves—generated by deep earthquakes should travel through the Earth's interior and bend smoothly due to refraction, leaving a wide "shadow zone" between 104 and 140 degrees of epicentral distance where no direct P-waves could be detected.

However, during the late 1920s and early 1930s, Lehmann meticulously analyzed seismograms recorded at station networks in New Zealand and Greenland following a major 1929 earthquake near Murchison, New Zealand. She observed unexpected, faint P-wave arrivals appearing directly within the predicted shadow zone. Rather than dismissing these anomalous signals as instrument noise or secondary crustal reflections, Lehmann constructed a rigorous geometric model. She hypothesized that an inner boundary existed within the core at a depth of approximately 5,100 kilometers. According to her calculations, P-waves striking this inner boundary at a steep angle would not merely pass through, but would be reflected and strongly refracted back upward into the shadow zone.

To verify her hypothesis without electronic computers, Lehmann performed manual calculations using ray-tracing geometry, assuming an inner core radius of roughly 1,200 kilometers and a sharp step-increase in wave velocity at the inner core boundary. Her theoretical travel times precisely matched the arrival times recorded by the Galitzin seismographs in Wellington and Christchurch. Although initial reception among European geophysicists was cautious, prominent American seismologist Charles Richter supported Lehmann's interpretation in 1938, and Harold Jeffreys formally incorporated the inner core boundary into global seismic velocity models by 1939.

According to the passage, from which location did Lehmann obtain the seismographic recordings that revealed anomalous P-wave arrivals within the predicted shadow zone?