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A personal account of the California Gold Rush from the point-of-view of the fictitious Thomas Hartley.

Cross-correlation of 1 month of ambient seismic noise recorded at USArray stations in California yields hundreds of short-period surface-wave group-speed measurements on interstation paths. We used these measurements to construct tomographic images of the principal geological units of California, with low-speed anomalies corresponding to the main sedimentary basins and high-speed anomalies corresponding to the igneous cores of the major mountain ranges. This method can improve the resolution and fidelity of crustal images obtained from surface-wave analyses.

We have discovered nonvolcanic tremor activity (i.e., long-duration seismic signals with no clear P or S waves) within a transform plate boundary zone along the San Andreas Fault near Cholame, California, the inferred epicentral region of the 1857 Fort Tejon earthquake (moment magnitude approximately 7.8). The tremors occur between 20 to 40 kilometers' depth, below the seismogenic zone (the upper approximately 15 kilometers of Earth's crust where earthquakes occur), and their activity rates may correlate with variations in local earthquake activity.

Leading edges of population expansion provide unique opportunities for individuals to elevate their social and economic status. However, dispersal into unknown areas may have high costs such as violence associated with conflicts over resources, unfamiliar and harsh ecological conditions, and a loss of social networks. We investigate the background of men who dispersed to Gothic, Colorado during the late 19th century to prospect for silver ore. We find support for the hypothesis that men who chose to disperse to the frontier and endure such costs were on average those who lacked access to critical resources in their childhood homes. Yet contrary to this hypothesis and previous dispersal research, some migrants came from very wealthy and high status families. The incentives of long-distance dispersal to ephemeral mining towns with potentially high payoffs are different from the incentives of dispersal sites examined in previous literature. This project draws attention to the need to study heterogeneous incentive structures for dispersal and is also a small piece of understanding the larger puzzle of the colonization of frontiers and population expansion.

1. Natal dispersal distance (NDD; the distance between natal site and recruitment site) was studied in relation to proximal factors including sex, cohort, recruitment age, nesting density, nest site quality; and also within-colony movements of prospecting prebreeders among 133 recruits of two cohorts (1979-80) in a large, dense colony of western gulls Larus occidentalis (Audubon) on South-east Farallon Island, California. NDD was also studied in relation to ultimate factors, assessed from total number of chicks fledged to 1994, survival of breeding adults, and fitness-related life history traits, including brood size and hatching date. The Farallones colony is an unusual case in that it includes 50% of the species population and 90% of all western gulls breeding within a radius of 1000 km. Hence, potential recruits could choose between locations within the Farallones colony, but had limited choice to recruit at other colonies. 2. Among prebreeders, distance from natal site to prospecting site increased with age among gulls aged 2 to 4 years, and stabilized in 4- to 8-year-olds. Most 2-year-olds prospected on their natal sites. 3. Compared to other bird species, natal philopatry was strongly developed in both sexes, but was significantly greater in males (median distance between natal and recruitment site among males, 17 m; median distance among females, 50 m). 4. More philopatric males nested in areas of higher density and with a tendency for more nest cover (P = 0.080, when controlling for the effect of density). A non-linear relation between NDD and recruitment age among males resulted from shorter NDD in 4-, 5- and 6-year-olds compared to 3-year-olds and males older than 6 years. There was no relation between NDD and recruitment age in females. 5. Males who had hatched early in the season (individuals who were, on average, more dominant, with higher prebreeder survival and recruitment probability; Spear & Nur 1994) had shorter NDD than males who hatched later. 6. Fitness costs associated with natal philopatry were detected in both sexes. More philopatric males survived significantly less well than did less philopatric males. Average number of chicks fledged among experienced females (6-11 years breeding experience) was significantly lower among more philopatric compared to less philopatric individuals, as was cumulative number of chicks fledged for all females (as of 1994). 7. Thus, whilst philopatry was well developed in these gulls, the trait appeared maladaptive. This paradoxical result may be related to an extended period of poor food supply (1989-94) in the Gulf of the Farallones. We hypothesize that fitness costs associated with philopatry reflect different life history strategies where high philopatry may be part of a high effort strategy characterized by higher reproductive effort and lower survival. These results are consistent with the view that relative advantages and disadvantages between life history strategies could lead to selective equilibrium, depending on environmental conditions.

To complement the growing literature on magnetic prospection in historical archaeology, the practical aspects of magnetometer selection and survey design need to be explored. Based on a test case from the Petaluma Adobe State Historic Park in northern California, two readily-available magnetometers are compared with respect to instrument type (alkali-vapor versus proton precession), sensor configuration and number (total field versus vertical gradient), sensor height, intensity of data collection, and basestation correction procedures. These variables are then considered in light of survey speed, labor input, and monetary cost. Results indicate that the alkali-vapor gradiometer is better suited for historical archaeological research based on survey speed and efficiency, volume of data collected, temporal and spatial intensity of station readings, and sensor sensitivity. In addition, the data reconfirm the importance of sensor height, gradiometer configuration, and basestation correction in obtaining high-quality magnetic data.

Public interest in hunting for gold washed into California's streams in the lower Sierra Nevada area has increased. The price of gold is approaching $400 an ounce and heavy rains have increased the presence of flakes in the streams.

Public interest in hunting for gold washed into California's streams in the lower Sierra Nevada area has increased. The price of gold is approaching $400 an ounce and heavy rains have increased the presence of flakes in the streams.