Hawaii is one of the most active volcanic regions in the world, with the long-lived Pu'u' O'o-Kupaianaha eruption of Kilauea continuing since 1983. The magmatic activity is accompanied by high rates of earthquake activity and Hawaii has great value as a natural laboratory for studying the interactions between magmatic and tectonic processes. The seismic network operated by the U.S. Geological Survey (USGS) Hawaii Volcano Observatory (HVO) records thousands of events every year and since 1986 a substantial database of earthquake waveforms has accumulated. This project will involve analyses of these data to improve earthquake location accuracy and to resolve more details of earthquake source processes, such as the amount of stress that is relieved during faulting. The PIs will adopt a number of new methods that have been used successfully in the analysis of southern California seismicity and apply them to the Hawaiian dataset. The results from this study are expected to yield a sharper view of fault zone characteristics as well as generate a public database of information suitable for other researchers in their work at Hawaii.
This project is a collaboration among U.C. San Diego, the University of Hawaii, and USGS HVO to apply a variety of newly developed seismic techniques to analyze waveforms from ~200,000 earthquakes recorded by the HVO seismic network in one of the most active volcanic regions in the world. These methods promise to greatly improve event location accuracy and to provide robust estimates of the patterns of earthquake stress drops, results that will help characterize fault-zone structures at Hawaii and help resolve the relationships between seismicity, volcanic activity, and strain transients. Our results will address the following questions: (1) Relocated microearthquakes in Hawaii will likely align along resolvable fault and/or conduit structures: what do these structures reveal about the tectonic and volcanic processes? (2) Are there repeating earthquakes with nearly identical waveforms, and can they be used to resolve temporal variations in seismic velocity associated with tectonic and volcanic activity? (3) How do the stress drops of Hawaiian earthquakes compare to other regions? Are there variations in earthquake stress drops that can be used to characterize stress field heterogeneity and identify regions of stress concentration? (4) Are earthquakes at Hawaii self-similar, such that average stress drop is constant with event size and large earthquakes are simply scaled up versions of smaller earthquakes? (5) What is the space/time evolution of seismicity at Hawaii? Are there consistent temporal variations in seismicity and earthquake properties related to ongoing volcanic activity and strain transients? How much of the observed clustering in the earthquake catalog can be explained by mainshock/aftershock triggering models (e.g., ETAS) and how much reflects possible physical triggers such as fluid migration or slow slip?
The analysis and interpretation of earthquakes and other seismic sources from deep within Earth’s crust and upper mantle up to the surface play a key role in understanding how volcanoes work. Hawaii Island is one of the most tectonically, volcanically, and seismically active regions on Earth. The USGS Hawaiian Volcano Observatory (HVO) operates a seismic network that has recorded over 260,000 earthquakes since 1986, but this rich dataset has not been fully exploited. This project supported collaboration between HVO and U.C. San Diego to apply a number of new large-dataset processing methods to learn more about seismic activity on Hawaii and its relationship to faults and volcanoes. The results from this study provided a sharper and more comprehensive view of fault zone characteristics and generated public databases of high-resolution information on seismicity characteristics, suitable for other researchers in their studies of Hawaiian geology, tectonics, and volcanism. Important results include detailed images of earthquakes along the detachment fault that underlies much of eastern Hawaii and discovery of two ring-shaped seismicity features. This research is described in two journal publications so far, and has provided improved descriptions of seismicity and tectonics for Hawaii, which is helping our ability to monitor and characterize volcanic and earthquake hazards.
