Terrestrial v. Lunar Seismology: Challenges and Upcoming Technologies
The Earth and Moon, while entwined as a pair, couldn’t be more different from the view of seismologists. On Earth, seismologists dig holes, put a seismometers directly on nice hard bedrock, and record clean broad-spectrum signals (0.001-100Hz) of strong earthquakes. We can see clear seismic records of many distinct seismic waves that arrive one after another.
On the Moon, Apollo astronauts gently placed sensors on loosely consolidated regolith. The four Apollo Passive Seismic Experiment (APSE) seismometers recorded moonquakes as many long series of noisy, high-frequency (1-20Hz) signals in which no single wave is clearly dentifiable from another. Quake amplitudes were often recorded with only 1-10 digital units, making records even harder to interpret. Many spikes (possibly due to electromagnetic noise), contaminate the data. Despite the limited supply and many challenges of the APSE data, lunar seismologists have made key observations regarding the structure of the Moon and the nature of moonquakes.
With new and improving technologies, such as MicroElectroMechanical Systems (MEMS) accelerometers, it may be possible to rejuvenate planetary seismology. NASA and other space agencies already employ MEMS accelerometers in navigation systems, so the technology is proven. With only a few grams per axis as a scientific payload, and low power consumption, why not include a seismometer on every future mission landing on any planet? The only hurtle is tuning the right sensor for the right range of motions for the right planet.
Dr. Lawrence works in the field of structural seismology, particularly as it applies to deep Earth structures and the evolution of continents. His group focuses on the development of computational techniques to build models of the Earth and the Moon’s structure in order to address outstanding geophysical problems. Specifically, his work addresses the structure and dynamics of Earth’s mantle; imaging the anelastic structure of the Earth; and imaging the crust and lithosphere, and understanding wave scattering in the Moon. Jesse’s group also operates the Quake-Catcher Network, the world’s largest strong-motion seismic network built by connecting inexpensive seismic sensors to internet-connected computers. With more data, we hope to gain better understanding of earthquake ruptures and how earthquake energy focuses and defocuses in the Earth.