Source process of the 2002 Denali fault earthquake compared to other large strike slip events

Fromm, Robert
Özacar, Atilla Arda
Beck, Susan L.
Christensen, Douglas
The November 3, 2002 Denali Fault earthquake which is the largest inland event ever recorded in central Alaska, occurred along an arcuate segment of the right-lateral strike-slip Denali Fault. We use fi rst motion P-wave polarities and the inversion of teleseismic P-waveforms to constrain the focal mechanism and rupture history. We fi nd clear evidence for a substantial reverse component at the beginning of the rupture, which can not be explained with a pure strike-slip mechanism. This initial subevent occurred along an asperity 20 km west of the hypocenter and can be attributed to thrusting along the Susitna Glacier Fault. Approximately, 10 sec after the fi rst asperity failed, the rupture propagated unilaterally to the east on a strike-slip fault and released most of the seismic moment along an asperity located 170 km east of the hypocenter, adjacent to the rupture transfer from the Denali Fault to the Toschunda Fault which bifurcates toward the southeast. This earthquake had a duration of ~120 sec and a total rupture length of ~320 km with a maximum slip of 8 m. Correlation with gravity anomalies suggests a relation between moment distribution and physical properties of the subsurface rock units that may support a weaker middle segment marked by fewer aftershocks. Moreover, both asperities coincide with intense gravity gradients possibly refl ecting a crustal boundary. We analyzed the aftershock distribution by estimating the number of events, released moment, and b-values within regular spaced bins along the rupture plane. Strong correlation with the obtained asperities and weakness zones are observed, suggesting different aftershock nucleation mechanisms for different segments of the fault. Comparison of this event with similar magnitude November 14, 2001 Kunlun earthquake (Tibet) in terms of rupture length, aftershock distribution, radiated energy, static stress drop, and tectonic setting; implies a stronger seismic coupling along the Denali fault. For a broader approach, large (Mw > 7.2) strike-slip earthquakes with well-defi ned source parameters, are classifi ed on the basis of their location with respect to plate types and boundaries into three categories: interplate, oceanic intraplate and continental intraplate events. Each category is characterized by distinct patterns in terms of source parameters indicating that stresses are high for oceanic intraplate, moderate for continental intraplate and low for interplate events. In this respect, both the Denali and the Kunlun events are exceptional and have an interplate signature. In particular, the Denali Fault is an ancient suture between accreted litho-tectonic terranes which might indicate less strain hardening and cause this non-typical behavior.
IRIS - UNAVCO Joint Workshop


Source process of the 3 November 2002 Denali fault earthquake (central Alaska) from teleseismic observations
Özacar, Atilla Arda; Christensen, DH (American Geophysical Union (AGU), 2003-06-25)
[1] The November 3, 2002 Denali fault earthquake, which is the largest inland event ever recorded in central Alaska, occurred along an arcuate segment of the right-lateral strike-slip Denali fault. We use first-motion P wave polarities and inversions of teleseismic P waveforms for a fixed focal mechanism to constrain the rupture process. We find clear evidence for a substantial reverse component near the hypocenter at the beginning of the rupture. Twenty-five seconds later, rupture propagated unilaterally t...
Characteristics of the 2020 Samos earthquake (Aegean Sea) using seismic data
Kiratzi, Anastasia; Papazachos, Costas; Özacar, Atilla Arda; PINAR, ALİ; Kkallas, Charis; Sopaci, Eyup (2021-01-01)
The 30 October 2020 Samos earthquake (Mw 7.0) ruptured an east–west striking, north dipping normal fault located offshore the northern coast of Samos Island, previously inferred from the bathymetry and regional tectonics. This fault, reported in the fault-databases as the North Samos and/or Kaystrios Fault, ruptured with almost pure dip-slip motion, in a region where both active extension and strike-slip deformation coexist. Historical information for the area confirms that similar ~ Mw7 events had also occ...
The 2002 Denali fault and 2001 Kunlun fault earthquakes: Complex rupture processes of two large strike-slip events
Özacar, Atilla Arda (Seismological Society of America (SSA), 2004-12-01)
We studied the source processes of two large continental earthquakes, the 3 November 2002 Denali fault earthquake and the 14 November 2001 Kunlun fault earthquake, associated with strike-slip faulting along ancient sutures. We inverted teleseismic P waveforms using a pulse-stripping method for multiple time windows with different focal mechanisms and derived composite source models. According to our results, the 2002 Denali fault earthquake began with initial thrusting (M-W 7.3) along a 40-km-long segment o...
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There are many sources of flooding of river basins and coastal areas such as precipitation, tsunami, and storm surge. When assessing the risk of these hazards, it is important to understand the source but also to define the flood plain characteristics considering links between elements of flood plain. Although numerical hydraulic models are widely used to evaluate the risk quantitatively, description of the multiple links between exposure and susceptibility of a specific location or po...
Producing tsunami inundation maps: The California experience
Borrero, J; Yalçıner, Ahmet Cevdet; Kanoglu, U; Titov, V; McCarthy, D; Synolakis, CE (2003-01-01)
More than 20 tsunami events have impacted the State of California in the past two centuries. While some earlier 19th century reports are subject to interpretation, there is little question that offshore seismic sources exist and could trigger tsunamis directly or through coseismic submarine offshore landslides or slumps. Given the intense coastal land use and recreational activities along the coast of California, even a small hazard may pose high risk. California presents nontrivial challenges for assessing...
Citation Formats
R. Fromm, A. A. Özacar, S. L. Beck, and D. Christensen, “Source process of the 2002 Denali fault earthquake compared to other large strike slip events,” presented at the IRIS - UNAVCO Joint Workshop, YOSEMITE, Amerika Birleşik Devletleri, 2003, Accessed: 00, 2021. [Online]. Available: