Normal mode splitting functions

thingiverse

Similarly to when a bell is hit and standing wave patterns produce a sound, large magnitude earthquakes (typically magnitude 7.5 or larger) create standing waves on Earth that can be measured using seismometers. The vibrations from these standing waves can be related to the material inside the Earth, just like the sound of a bell or music instrument depends on its material and string thickness. When a massive earthquake occurs, it excites multiple standing waves, much like different notes on a musical instrument. We identify these waves using two numbers: radial order n and angular order l, which help us understand how they vary at different depths within the Earth. The Earth is not a perfect sphere; its structure varies with depth and location due to plate tectonics and mantle convection. This means that when we measure frequency variations in different locations, we get distinct patterns, similar to those seen on a cracked bell. These differences are visualized as splitting function maps, which help us map out how structures inside the Earth change. By analyzing normal modes sensitive to different depths, researchers can uncover secrets about the Earth's interior and its dynamics. Here, we present 3D-printable models of three normal modes that reveal distinct patterns in their frequency variation maps: * **Normal mode 0S26**: This normal mode is sensitive to structures in the upper mantle (50-500 km depth). High frequencies are seen under Southeastern Asia and South America, areas known for deep subduction, where cold material accumulates. Low frequencies are observed under central Africa and Afar, regions thought to contain hot, slow-moving material. * **Normal mode 2S16**: This normal mode is sensitive to structures in the lower mantle (2000-3000 km depth). Very low frequencies are observed under the Pacific and Africa, areas with low seismic velocities and hot material. High frequencies are seen in a ring around the Pacific, likely due to cold material from the Earth's surface. * **Normal mode 13S6**: This normal mode is sensitive to structures in the inner core (5150-6371 km depth). Its unique pattern resembles a squashed sphere at the poles, with high frequencies at the equator and low frequencies near the poles. This characteristic pattern has been interpreted as resulting from direction-dependent velocity variations within the inner core. All globes come in two halves that can be printed without support. They can be glued together using superglue after printing. Note that mode 02s16 allows for optional neodymium magnets to be inserted during printing, which can demonstrate its 180-degree rotational symmetry. However, if you choose not to use this feature, the globe will still print successfully with minor modifications.