Serpent Spirit-power Stories along the Seattle Fault R. S. Ludwin1 , C. P. Thrush2 , K. James3 , D. Buerge4 , C. JonientzTrisler5 , J. Rasmussen6 , K. Troost1 , and A. de los Angeles7 INTRODUCTION The Seattle Fault is a multistranded east-west-striking reverse fault cutting across Puget Sound, through downtown Seattle, and across Lake Washington. Although geophysical evidence has long indicated a substantial offset in basement rocks beneath Puget Sound (Danes et al., 1965), no clear pattern of recent earthquake activity defining the fault has been observed. Geologic evidence of an earthquake around A.D. 900 (estimated magnitude 7.3) came to light in the early 1990’s (Bucknam et al., 1992), however, and the Seattle Fault is now recognized as a substantial hazard to the Seattle urban area. The circa A.D. 900 earthquake caused 7 m of vertical uplift on the southern side, sent massive block landslides tumbling into Lake Washington, and created a tsunami in Puget Sound that left sand deposits on Southern Whidbey Island (Atwater and Moore, 1992). Two archaeological sites near Seattle attest to the effects of such events on local indigenous communities. Excavations at West Point, a promontory jutting out into Puget Sound north of downtown that was used as a fish- and shellfish-processing site since at least at least 4,000 years before the present, show that that the area dropped at least a meter during the quake. The point’s marshes were flooded with saltwater and a layer of sand covered the entire site. Over time, people returned to West Point and began using it as they had before the quake (Larson and Lewarch, 1995). The earthquake also had the capacity to transform some locales permanently. At the Duwamish No. 1 archaeological site, excavations show that the quake lifted up a low, wet area that had been only a minor camping and food-processing site and turned it into a higher, drier spot that eventually became home to a major permanent settlement with several longhouses (Campbell, 1981; Blukis Onat, 1987). Native peoples described and commemorated geologic events in their oral traditions by using descriptive metaphors based on their cultural concepts, often ascribing earth shaking to actions of supernatural beings. In this paper we discuss stories about a’yahos, a supernatural spirit power that natives associated with five locales along the trace of the Seattle Fault. Three of these locales are associated with landslides, and another has a description of offset consistent with the movement of the Seattle Fault. In 1985, prior to published evidence of the A.D. 900 earthquake on the Seattle Fault, an article in the Seattle Weekly (Buerge, 1985) mentioned a “spirit boulder” associated with earthquakes and landslides located near the Fauntleroy ferry dock in west Seattle. The proximity of this location to the Seattle Fault invited investigation, and we discovered that the Fauntleroy spirit boulder is associated with a supernatural being called a’yahos, which is often described in a way that could refer to earthquake effects and particularly landslides. The a’yahos is a shape-shifter, often appearing as an enormous serpent, sometimes double-headed with blazing eyes and horns, or as a composite monster having the forequarters and head of a deer and the tail of a snake (Mohling, 1957). A’yahos is associated with shaking and rushes of turbid water and comes simultaneously from land and sea (Smith, unpublished notes). “At the spot where a’yahos came to a person the very earth was torn, land slides occurred and the trees became twisted and warped. Such spots were recognizable for years afterward” (Smith, 1940). Figure 1 shows an artifact from a non-Salish tribe on the outer coast of Washington that corresponds to the description of a’yahos and represents a vicious guardian spirit. Stories about a’yahos mention a number of specific locales in the central Puget Sound, along the Hood Canal, and on the Strait of Juan de Fuca as far west as the Elwha River. Thirteen a’yahos locales are mentioned in various stories (Figures 2 and 3). While some locales are identified precisely, rather general location descriptions (e.g., “Dungeness River”) are given for others. A’yahos sites appear to coincide generally with shallow faults around the Puget Lowland, including the Little River Fault along the strait of Juan de Fuca, the Seattle and Tacoma Faults, and the Price Lake scarps (Haugerud et al., 2003). Five of the a’yahos story sites are spatially concentrated and located very close to the trace of the Seattle Fault (Figure 3). Four of the Seattle locales can be associated with land- 1. Department of Earth and Space Sciences, University of Washington 2. Program on the Environment and Department of History, University of Washington 3. Anthropologist 4. Historian 5. FEMA 6. Duwamish Tribe cultural resources expert 7. Snoqualmie Tribe cultural resources expert and great-grandson of James Zackuse, Duwamish Indian doctor Seismological Research Letters July/August 2005 Volume 76, Number 4 427 ▲ Figure 1. A Quileute ceremonial representation of a two-headed horned serpent with legs; known as a vicious guar
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Dating the 1700 Cascadia Earthquake: Great Coastal Earthquakes in Native Stories (PDF)
Dating the 1700 Cascadia Earthquake: Great Coastal Earthquakes in Native Stories Ruth S. Ludwin1 , Robert Dennis2 , Deborah Carver3 , Alan D. McMillan4 , Robert Losey5 , John Clague6 , Chris Jonientz-Trisler7 , Janine Bowechop8 , Jacilee Wray9 , and Karen James10 INTRODUCTION Although scientific recognition of the earthquake hazard presented by the Cascadia subduction zone (CSZ) is relatively recent, native peoples have lived on the Cascadia coast for thousands of years, transferring knowledge from generation to generation through storytelling. This paper considers the ways in which information on coastal earthquakes is presented in native traditions and estimates the date of the most recent event from them. The primary plate-boundary fault of the CSZ separates the oceanic Juan de Fuca Plate from the continental North America Plate (Figure 1). It lies about 80 km offshore and extends roughly parallel to the coast from the middle of Vancouver Island to northern California. Although recognized as early as the mid-1960’s, the CSZ was initially assumed to be incapable of producing great megathrust earthquakes. It is seismically quiet, and no sizable earthquake has occurred on it since European settlement began. As the theory of plate tectonics matured, studies of subduction zones worldwide identified characteristics associated with megathrust earthquakes. These earthquakes are most common in areas where hot, young, buoyant crust is rapidly subducted (Heaton and Kanamori, 1984). Although the rate of subduction in Cascadia is relatively slow, the subducted crust is among the youngest and hottest anywhere. Field investigations soon located geological evidence of abrupt land-level changes characteristic of megathrust earthquakes in “ghost forests” of dead cedar trees in coastal estuaries in Washington and Oregon (Nelson et al., 1995). The cedars, originally above the limit of the tides, were killed when their roots were suddenly plunged into salt water. Beneath the surface of these same estuaries, soil cores revealed layered deposits showing a repeated cycle of slow uplift and rapid submergence. Preliminary age estimates based on radiocarbon dating (Nelson et al., 1995) and treering studies (Yamaguchi et al., 1989) suggested that the most recent earthquake happened about 300 years ago. The exact date and approximate time of the most recent CSZ earthquake, 9 PM on 26 January 1700, were determined from Japanese historic records of a tsunami arriving with no reports of associated shaking (Satake et al., 1996). The year was con- firmed through close study of tree-ring patterns of ghost cedar roots (Yamaguchi et al., 1997). The magnitude estimate of 9.0 implies rupture along the entire length of the CSZ (Satake et al., 2003). Figure 1 shows the geographic extent of the likely rupture area. TRADITIONS FROM CASCADIA At the time of initial European contact, Cascadia native groups spoke more than a dozen distinct languages (Thompson and Kinkade, 1990) and lived in a complex social landscape with both similarities and differences between groups. Collection and recording of native stories began in the 1860’s, more than 350 years after the first European contacts in North America, almost 100 years after initial contact in Cascadia, and nearly 50 years after European settlement began. As a result, as much as 95% of native oral traditions may have been lost (Jacobs, 1962), and available recorded examples may not be a representative sampling of the original material. Storyteller, transcriber, and language and cultural issues all affect the story that ends up in print. Nonetheless, versions of oral traditions are preserved in hundreds of sources, and numerous stories describe shaking or marine flooding. Artifacts, dances, songs, ceremonies, and personal and place names supplement the range of information available for study. We are deeply indebted to the many informants who shared their stories and allowed them to be preserved in written form. Figure 1 shows source locations for 40 native stories from 32 independent sources. These stories represent less than a third of the known stories that refer to shaking or marine 1. Department of Earth and Space Sciences, University of Washington 2. Huu-ay-aht First Nation 3. Carver Geologic, Inc. 4. Department of Anthropology, Douglas College 5. Department of Anthropology, University of Alberta 6. Department of Earth Sciences, Simon Fraser University 7. FEMA Region X 8. Makah Museum and Cultural Center 9. Olympic National Park 10. Bainbridge Island, Washington Seismological Research Letters March/April 2005 Volume 76, Number 2 141 flooding and were selected on the basis of clarity, descriptions of phenomena notable in megathrust earthquakes, and geographic distribution. Some of these stories have been discussed in earlier studies (Heaton and Snavely, 1985; Clague, 1995; Carver and Carver, 1996; Minor and Grant, 1996; Hutchinson and McMillan, 1997; Losey, 2002; McMillan and Hutchinson, 2002). Figure 2 tabulates story elements and gives date estimates. Stories referenced in Figures 1 and 2A have been broadly grouped into three time categories: stories from which dates can be estimated, stories that are clearly historical but impossible to date, and apparently mythic stories without any clear timeframes. Historical stories cannot be distinguished from myth by style or content alone, however (story ref. 23, p. ix), and stories that appear to be mythological may be based on historical events. Stories designated as historical in the source texts are identified as historical in Figures 1 and 2A. Stories vary considerably in content and style along the Cascadia coast. At the southern end, many stories explicitly mention both earthquakes and tsunami. At the northern end, there are explicit earthquake stories and explicit flood stories, but only a few stories including both phenomena. In the middle portion of the CSZ, along the coast of Oregon and Washington, direct mention of earthquakes is rare and stories of marine floods are common. The differences likely result from differences in the collection and preservation of stories, and may also reflect differences in native cultures and lifestyles along the Cascadia coast or variations in earthquake effects. HISTORICAL TRADITIONS Nine